Agree, certainly.  There might be a way to sort of carry over my knowledge from EM radiation.  I just do not see it yet.  If one substitutes for accelerated (to3rd derivative) charge to accelerated mass, it cannot be done with "force" because the only force on a mass is the equal and opposite reaction of an equivalent mass impulse at the same point.  Therefore we get into having to do it with the gravitational field itself, to accelerate the masses ... which is sort of like using an EM field to accelerate charges to get them to radiate.  Well, such an EM field is radiating to begin with, so the charges are just scattering or modifying it.  Hmm...

I have an idea.  Suppose + and - charge objects are scattered off each other.  The EM radiation from that should be similar to gravitational radiation.  It is not a problem I've ever looked at, but when I get back in town I will give it a try.

Robert,

I am partial to the gravitational concept that gravity is caused by massive particles of all sizes, from photons to neutrinos to colliding rocks; all scales of matter that move through space are the source of gravitational effects. It may be that the constituents of zero point energy also play a role, which is not clearly understood yet. The aspects of this model that appeal to me are the explanations about why the universe seems flat, why there is outward expansion at the edges of the universe, why gravity does not emanate from a massive body, but rather is the net effect of random collisions. I have often wondered if "gravitational waves" are simply the study of the macroscopic effects of the random collisions that I have mentioned?

Frank

In my quantification of the Aether, it can be seen that Aether has five dimensions of freedom, as opposed to the four dimensions of space-time. The gravitational waves are displacements of Aether, not matter, which is why no object can affect the gravitational waves.

Think of a world with three dimensions of area-time. A flexible television screen would be an example of an area-time world. Someone in the four dimensional world of space-time wiggles the flexible television screen and causes the equivalent of a gravitational wave. The gravitational wave can easily be seen from the space-time perspective, but it is completely unnoticed in the area-time world. 

This is exactly why laser interferometers in space cannot detect gravitational waves. The interferometers exist in a four-dimensional space-time world, but the gravitational waves exist in a five-dimensional space-resonance world. 

The only way to detect the presence of gravitational waves from a four-dimensional world is to find a structure that exists in both the four-dimensional and five-dimensional worlds. The Aether is the only five-dimensional structure. 

Modern physics tells us the Aether does not exist. Actually, Einstein never doubted the Aether, but merely claimed he could describe physics without it. For the most part, he could. But the Aether is not only real, it is the foundation upon which the whole physical Universe exists, much like a canvas is the foundation of a painting. One can explain a painting without mentioning the canvas, but the canvas is necessary, nonetheless.

The Aether is actually observable in modern physics in the form of magnetic, electric, and gravitational fields. It is also observable via particle half-spin, solitons, positive holes, photons, and several other important effects caused by the presence of a quantifiable space, which interacts with matter.

The magnetic structures of an magnetically strong star, such as our Sun, tend to erupt when gravitational waves pass through the star. During the strong solar cycles I was following about one gravitational wave per day as indicated by a certain pattern of solar x-ray flares. A few years ago, there were other scientists working with NASA pursuing the same observations and for the same purpose, but they were too afraid to bring up the Aether in their quantifications of the events.

Before I can make further progress in this, I need to get MathCAD 11 or 14 programmed with custom units based on a new system of units I have developed. The cgs system of units might work, but modern physics has butchered cgs with all its square root units of charge. 

If you know someone who has the time and skill to produce a system of units based on distributed charge, which I have already laid out in a book, then we could wrap up many loose ends in physics very quickly, including gravitational waves. The unit system I have developed is named Quantum Measurements Units (QMU) and is a true five-dimensional system of space-resonance (three dimensions of length and two dimensions of frequency).

In this system, the Aether is a fundamental unit of physics equal to Coulombs constant times 16pi2. Every other unit is shown to be a factor of Aether.

How did we get the ether involved?  I did not ask about that.  And Frank, where did you get the idea that collisions and not objects cause gravity?

I have been on travel and suffering a bit of travel fatigue (severe actually).  In a few days I will follow up on trying to find EM quadrupole illustrations that may shed some light on gravity.  If anyone already has such insight, I would appreciate a post.  Thanks.

Dear Robert, from my standpoint the GW are emitted via transitions between gravitational energy levels with quantum numbers decreasing down to the ground state, likewise in the hydrogenlike atoms; by replacing –Ze^2 with -Gm^2 one finds the same Einstein formulae of -dE/dt and -dr/dt, but quantized. The quantum number n compatible with astronomical masses and distances results however very high; obvious then that a gravitational system decays down to the ground state, where no GW are longer emitted likewise as the atoms do not irradiate e.m. energy. More details are in the paper “Quantum approach to the gravitational waves” recently published. The connection between G and Ze is not merely formal: in this respect, let me suggest to your attention the section 5 of the paper “Diffusion equations, quantum fields and fundamental interactions” recently published. Best regards. Sebastiano

Article QUANTUM APPROACH TO THE GRAVITATIONAL WAVES

Article Diffusion Equations, Quantum Fields and Fundamental Interactions

Hi Minas ... you have given too advanced an answer.  I have no idea why 1-2 should be different than 3, in fact it looks like 3 is just one fractional orbit of 1-2 at closest approach.  Simply stating that they are different is not helping me.

Sebastiano, I'm sure your references would be interesting to someone seeking a QM understanding of GW, but without a classical understanding of the field pattern it would be like reading Greek or Farsi.

Robert,

The collision theory of gravity is not mine, but I think that it has merit. I first learned about it at a conference on gravity at the New York Botanical Gardens in the summer of 2001 and preparations leading to the conference. Isaac Newton, himself, was embarrassed by his inability to give a reasonable cause for his gravitational equations. Newton did not imagine that gravity was a force emanating from massive bodies. The collision concept is that particles randomly racing through the universe (neutrinos were discussed as a likely possibility at the conference, but I believe that any moving mass would contribute to gravitational effects) cause gravity with their collective net push generated by collisions with other objects in space. As, say, a planet and moon are near each other, the relative vacuum of particles between the planet and moon, due to their shadowing of collisions from each other, would create a net push toward each other. What I like about this theory is that it does not require a central force in a massive object (which has never been measured) nor does it require a "pull" force to reel objects in toward each other. (Even a trailer hitch pushes the trailer forward. The "pulling" is a macroscopic view of the trailer following the vehicle with the power source, which happens to be in front.)

Frank, I see what you mean.  But I do not see how it helps me to visualize a quadrupole radiation field, or the conditions for radiation.

Essentially QED is a collision theory.  Attractive forces are generated in a rather complex way partly due to uncertainty (it's not clear where virtual photons are) and the interaction of phase and charge sign.  I do not understand it well enough to explain it, but I have read enough to know it is a collision theory.  You can't use Feynman diagrams to understand attractive forces, though, and this causes many questions on the web.

I've actually spent some time thinking about a collision theory of gravity, I realize now that I see what you are talking about.  If you care to start a thread on it I'll participate.  It is interesting, but there are some issues.  A collision theory should lead to shielding.

Guys, my question and interest is about the field pattern and how it arises from the configuration and motion of macroscopic masses, *NOT* a question about quantum fundamentals.  Those answers are not helping me.  Thanks.

I'd recommend Kip Thorne's course: http://www.aei.mpg.de/~pau/GWs_Course.html. 

Stam, looks interesting.  Obviously will take some time to evaluate.  Thanks!

Robert,

I would like to follow-up on your suggestion to start a thread on a collision theory of gravity. Unfortunately, this isn't the time for me to do it. I'll need to get a few items off of my plate before doing that.

One comment in response to your remark about quantum fundamentals. If you were to look closely at the "Origins of Classical Matter" paper that Tom Kopinski and I have posted, you will find that our description of the smallest classical particles, neutrinos, photons, electrons and positrons were all developed without the need for reference to quantum fundamentals other than the idea that all particles, at the proper viewing scale may be considered to be discrete particles. We also do not refer to the current presumed quarks. The particle dynamics that we show are all produced with standard classical physics principles and an assumption about the nature of the aether or zero point background and an assumption about the physical properties of a new object, the Quantum Momentum Unit (QMU), which may be an alternative description of the Higgs particle.

Which leads me to this question: What do you imagine the medium to be that transmits gravity waves?

Hi Frank,

With regards to the structure of matter, anything relating to the standard model, and QM in general, I do not have deep skills.  I am fond of Asif's theory, if you're familiar with that, but cannot defend it.  I just like it because it dovetails with certain ideas of mine about inertia.  But I am not talking about Higgs particles or anything like that, strictly classical GR, gravity, relativity, etc.

Regarding the medium that transmits gravity waves, I have no opinion.  I do not even have an opinion on whether gravity waves exist.  They have not been detected, after all.  I believe the text book answer is that they propagate through space-time curvature changes, but I have some serious questions about what that is, as evident by all the working papers you'll find on my profile.  I can't very well address this question until I understand the established theory a little better.  The material Stam suggested looks interesting.

Frame dragging, or something like it, is another possibility for bleeding off energy from a gravitational system.  But I have not done any calculations.  I have just recently begun to realize frame dragging would occur in any gravitational theory, even in the Newtonian theory when adjusted for time dilation (which is an inevitable consequence of a universal action and energy conservation, though Newton did not have the Planck relation and could not have guessed it due to his notion of absolute time).

The weakness of a frame dragging sort of explanation of gravitational wave energy radiation is that it seems to be dependent on an average density of matter for propagation, i.e. it is the matter of the universe which, by gravitational linkage, propagates the wave.  It might not depend too much on nearby matter,

Robert> Essentially QED is a collision theory.

There is a big qualification to that. A system where forces are transmitted by exchange of real particles (real photons) experiences the Pointing-Robertson effect. I.e., forces which don't act in the radial direction (to sufficiently high accuracy), and hence don't conserve angular momentum (to sufficiently high accuracy).

In a particle exchange picture, the virtual photons responsible for the Coulomb interaction must already exist in a bound cloud around charged particles. 

A collision theory of gravity, with attraction due to shadowing, suffers from the same problems (actually slightly worse).

Kåre, that's an interesting bit of information, thanks.  BTW I've tried several appealing shadowing theories of gravity, but none I've seen or thought of really come very close.  For one thing, shadows would seem to imply shielding might be possible, which doesn't seem to be the case. 

Kåre and Robert,

In your studies of a collision theory of gravity, are either of you focused upon any particular scale of interaction? For example, are you focused upon any particular particle as an agent of gravity in the collision events?

Frank, I did not conduct a serious study, only thought about it on a few occasions.  I did not follow up because of the shadowing problem.  While I didn't define a specific particle, I was considering a wide range, including negative energy particles, and FTL particles.  Mass lost or gained (depending on whether positive or negative energy) would be replaced or subtracted from the absorption of particles from other bodies.  But that right there killed it, because absorption in such a manner would necessarily produce a shadow.

In my 2013 treatment, which is a bit incomplete as far as curved space-time is concerned, but could now in theory be extended to cover that, I used no intermediary particle, but direct interaction through the uncertainty of the gravitating particles or quanta themselves.  This avoids shadowing issues since it occurs behind the QM curtain, much like entanglement.  In fact, were I sophisticated enough in the application of QM (it would require more sophistication than the typical course offers, which I've had), I'd formulate gravity and inertia as a multi-body position-momentum entanglement.

Let me pose a slightly different version of the question, which at its root is about how and under what circumstances energy is transferred, radiated, detected by means of gravitational fields.

If one could reach into a system and move a large body about rapidly, say by a long idealized pole, then nearby, maybe even quite distant, masses would be influenced to move about slightly, and would absorb energy from your doing.  Is this considered gravitational waves?  If not what is it called, and was it accounted in the binary pulsar computation.  And in either case, would gravitational wave detectors detect it?  (I'm thinking probably not because it is very low frequency and long wavelength).

Robert,

Thank you for your two comments. While I find this topic very interesting, I don't have any clear answers. The answers that do appear, however create more questions. I'm going to say out loud some of my speculative thoughts on this subject. Take them with a grain of salt.

If gravity is a wave, then how does the wave push things around? My image of a wave is, say like an ocean wave, which has a frequency and oscillates between crest and furrow. I admit things do get washed ashore, but its not the wave action that does it but the cresting wave as it nears shore trapping objects in its surfers tube.

I also assume that objects cannot be pulled at a distance, but must be pushed, which is a point in favor of a collision model. I suspect that neutrinos are the most prevalent objects that interact with massive bodies to create what we call gravity, but by no means the only objects involved. The shielding problem that you describe can be explained by neutrinos being the primary gravitational object, because of the difficulty of detecting neutrinos. By the way, if it is true that neutrinos are a primary actor for gravity, then weight itself would be a neutrino detector. There is a difference between capturing the neutrino's interaction by some visible artifact, and feeling weight. Because of the size of neutrinos, visualizing the interactions may be a more difficult process than the neutrinos actually interacting with matter below our awareness. In a collision model, it seems to me that the neutrino does not necessarily need to have a an energetic interaction other than transferring momentum, which is also likely to be extremely difficult to detect for a single neutrino. However the net effect could be significant.

Frank, let me just clarify my question about gravitational waves, vs. the idea of gravity being a wave, and the analogy of pushing things ashore.  My understanding of the current theory of gravitational waves, which is all I am asking about, is that they are not the cause of gravity.  Gravity is the structure of some field, which can be static, and is generally thought to be space-time itself, but that is neither here nor there as far as my question is concerned.  Waves would just be disturbances in that field (or in space-time if one prefers), possibly detectable, and explaining the energy loss of decaying binaries.  But not explaining gravity itself.  So there is no requirement for waves to push or pull anything.  Instead, the usual supposition is that they stretch objects in one direction and compact them in another.  Two points need further clarification, I think:

• Since space-time effects everything, including time and light, then I do not really see how anyone expects gravitational wave detection to work.  The stretching effects, though they might be noticed by a distant observer, such as a slight change in the bending of light rays, maybe even a modulation of light angle, very slight, within a local area, by the equivalence principle, gravitational wave should be undetectable.  That's my naive thinking, so obviously I'm missing something.
• For purposes of quantum gravity, it is observed that if there are gravitational waves, it should be possible to quantize them, and this leads to discussions about gravitons, etc.  But most of these theories do not actually address the effects of static gravity (possibly excepting quantum loop gravity).

You may enjoy these simulations of gravitational waves. It shows how space is distorted using ThreeDimSim to physically model the foamy structure of space itself. 

http://www3.telus.net/foamyether/simulations-grav.html

Peter, thanks for the novel sim.  Two immediate reactions...

Since no one has answered my post on detection a few days ago asking essentially about point #2, I am starting to assume maybe no one on RG actually knows how a grav wave detector works.  I suppose we could also hold out the possibility the physicists designing them haven't heard of the Michelson-Morley experiment, but that seems unlikely.  Yes? Maybe?

Any takers on explaining how we can detect changes in the length of a rod if it is space that is changing so that the locally measured rod length doesn't actually change?

Robert,

1.    I completely agree with your feedback. I mass does not move back and forth on its own like I have in my simulation; it needs to belong to a binary system, hence the quadrupole waves. I made the simulation simple to show how the foamy ether can carry a gravitational wave. I will update my website to explain this (thanks).

2.    Agreed as well. The length of the rod and light ray, do remain constant, because the number of foam cells remain constant. That is precisely why Foamy Ether Theory (FET) predicts that interferometers are a fundamentally flawed method of detecting gravitational waves. They will never detect gravitational waves, just like the Michelson-Morley failed to detect motion through ether. The interferometers are great; it’s the theory behind it all that is flawed. (I believe that history is about to repeat itself).

I’ve included a link below that explains in detail how light slows down when space is compressed, and speeds up when space is stretched. This results in the two returning laser beams (of an interferometer) to always be in phase, even when a gravitational wave passes through. The gravitational red-shift and Shapiro time delay proves that this happens.

You may be interested in reading my article describing my design of a ‘time variance’ gravitational wave detector that is based on measuring changes in the rate of flow of time.

http://www3.telus.net/foamyether/introduction-gra.html

Peter, looks like we are on the same wavelength, then.  You are aware, I suppose, Einstein tried to re-introduce the terminology of an ether but was out-voted?

It should be possible to detect gravitational waves by other means, and I see that a time variance idea is at the root of your article you linked above.  That in theory should work, just the way we detect redshift.  I'm concerned about one thing, which is that the source of the shift in frequency in this case has to be taken on faith, because it is not static and lasting indefinitely.

Another method is by light bending.  But it wouldn't be local.  The light would have to be from a distant astronomical source that crosses through the region of space containing intense gravitational radiation. The background object should wiggle in time to the waves passing across its light trajectory.

Would be interesting to see a calculation of this and determine the range over which it would work or not.  Obviously it does work if the light of the distant star passes through the quasi-static portion of the field.  How about several orbital diameters away?  By this method also the speed of propagation might be confirmed.  I am not able to do the calculation using the full GRT.  I offer the suggestion to you for a paper idea if you are able.

Robert,

I am aware that SR made ether unnecessary, but Einstein could not imagine GR without it. I guess university professors don’t like to tell their students that there is no ether, then ten years later, tell them there is!

I’m not sure what you mean by “I'm concerned about one thing, which is that the source of the shift in frequency in this case has to be taken on faith, because it is not static and lasting indefinitely.“ We experience static (steady) time dilation on the surface of the planet because of the earth’s gravity (defined by GR). But a gravitational wave passing through the earth will cause the strength of this gravity to fluctuate, thereby causing time dilation to fluctuate in tune with the wave. This will cause the laser’s wavelength to fluctuate as well.

Your method of measuring the “wiggle in time” of the light from a background object sounds much like what’s already being done by ‘pulsar timing array’ projects (https://en.wikipedia.org/wiki/Pulsar_timing_array). This involves making precise measurements of the arrival times of radio waves emitted by pulsars. Gravitational waves between the pulsar and us are theorized to affect their arrival times.

https://en.wikipedia.org/wiki/Pulsar_timing_array

Peter,

Yes, I suppose the time variation is a sort of wiggle.  I noticed that there was little overlap of detector ability (signal to noise ratio) and source strength.

Regarding your question about what I meant, it takes a bit of explaining but it is not complicated.  However, I am not sure how or if it applies to waves, so I'll just dive into the explanation.

Einstein used a steady state argument that wavefronts could not be indefinitely accumulated in or drained from the transmission medium, and so a steady state measured clock rate is the actual rate of the remote clock. 

This would not apply to clock variations from gravitational waves, transient variations in the space-time curvature, or potential.  If you are looking at a microwave signal from a clock a few kilometers away, in principle the space and time variations could be compensatory.  The clock could run a little slower at the same moment that the distance to the detector was contracting, accelerating the wavefronts and concealing the speed of the clock, for example.  Since the effect is transient, as the space relaxes to normal slowing the wavefront rate the clock speeds up canceling it.  This can repeat over and over indefinitely.

I do not know the details, i.e. now to write a dynamic metric for a gravitational wave.  The opposite could also happen, exaggerating the clock changes.  Or simply moving them by some phase angle.

It seems to me to be difficult to say precisely what happens to distances when a gravitational wave passes.  In a static field, we have the circumference, which we presume is unaffected and which provides a coordinate reference that either local or remote observers can use to find the invariant coordinate radius.  Let's say we are adding or subtracting mass to a central attractor.  The proper distance to the attractor increases with mass.  The circumferences allow us to fix the end points for measurement.

For sake of understanding the geometry, suppose the mass were varying.  Of course it cannot.  If it could, a monopolar wave would result.  Not even EM fields do this (except in a sort of near-field sense using the Earth as a ground plane reservoir).  But if a clock were tied to a circumference very close to the attractor, and an observer tied to a circumference much farther away, both the proper distance between them and the clock rate would be time varying, and both would modulate the frequency of the received signal.

If you have a clock close to the point in space where two stars will approach closely in their mutual orbits, and a distant observer, then the same thing would happen.  The proper distance to the distant observer would vary.  The distant observer, if very distant, can be fixed in position using a circumference about the center of mass of the binary system (I presume).  I don't know how to fix the position of the clock, however.

Perhaps you have already thought this through.  If so, I'd be very curious what your analysis says.

Robert,

I believe you are correct in saying that the ‘proper distance’ varies as a gravitational wave passes. This is demonstrated in my simulation in Figure 40. You can see that the number of Planck cells between the moving mass and the detector varies with the wave; the cyan colored tracer follows the path of a cell.

Your thought experiment of a ‘microwave signal from a clock a few kilometers away’ is intriguing, however. This would be similar to the experiment where microwaves were bounced off the planet Mercury to measure the Shapiro time delay. The returning microwaves become more and more delayed as Mercury approaches the Sun.

Keeping this model in mind, we can compare it to a distant (and stationary) Pulsar emitting periodic pulses of EM waves. If a black hole happened to travel across (or near) our line of sight, the incoming pulses would experience a momentary (Shapiro) delay in their arrival times.

The ‘space and time variations could be compensatory’, as you say. This would result in the wavelength of the EM waves being unchanged, however their arrival times (or phase) would be delayed momentarily (implying that they had a greater distance to travel).

The space-time distortion caused by this transiting black hole would be similar to a transiting gravitational wave. Measuring variations in the arrival times of EM waves from an array of Pulsars should prove the existence of gravitational waves (or transiting astronomical objects).

I hope that this is the explanation you are looking for.

http://www3.telus.net/foamyether/simulations-grav.html

Your simulations are certainly interesting.  But they raise questions in my mind about exactly how the physical objects respond to the waves, and why they do or do not move with the local cell they are in.

In special relativity, for example, you can accelerate this way or that, and you see the space in which an inertial system resides with lengths changed and clocks skewed in different directions.

But if you accelerate the [formerly] inertial system, the clocks will not be synchronized, the lengths if objects are not materially connected will not be right, and it will be unsuitable for making Einstein measurements - which one can easily detect.

If the passing of a gravitational wave makes a system non-inertial ... how does it do that?  That's something that heretofore I believed gravity could not do.   But if it remains an inertial system, how can it detect any change in the space-time in which it exists?  That would violate the equivalence principle.  Of course it's possible to detect tidal forces with a sufficiently large detector, but I have seen no actual claim there are tidal forces in a gravitational wave.  And all detectors, even the proposed orbital ones, are practically microscopic on the astronomical scale of things.

In FET, there are no ‘physical objects’ as described by mainstream atomic models. The only thing physical is the foamy ether (in a void) and so-called atomic particles are knots or distortions in the foam, which cause the surrounding foam to be distorted as well. A knot (particle) in the foam will be affected if hit by a wave because they are both distortions in the foam. Figure 6 shows how a knot (particle) travels through the foam. I realize that the simulations are somewhat limited and not inclusive of all forces at all times, but I had to start somewhere. This is why I don’t claim to have a complete TOE with mathematical rigor and all, but rather a ‘Framework’ for a TOE. FET offers a starting point for an actual ‘physical model’ for the underlying structure of matter and space-time; something which is seriously lacking in QM and GR, which are based on pure mathematics. (Lots more work needs to be done.)

I would say that gravitational waves ‘do’ contain tidal forces. I think that if you were positioned too close to a binary black hole system, the tidal forces from the waves would rip your spaceship apart; no different than if you did too close of a flyby of a black hole. There’s not much difference in you traveling through a changing gravitational field or a gravitational wave traveling through you.

Tidal forces, I believe, is why interferometers won’t detect gravitational waves. Testing the detector involves wiggling the mirrors with a sample signal. This is not sufficient proof that the detector actually works because the space between the mirror and photo detector is not altered (stretched or compressed) like it would if a gravitational wave was passing through.

http://www3.telus.net/foamyether/matter.html

Peter, thanks for the explanation and discussion.  You might be interested in a question John Macken just posted on how to visualize photons.  Anyway, I would be curious as to how you'd answer it.

RS: Let me pose a slightly different version of the question ... If one could reach into a system and move a large body about rapidly, say by a long idealized pole, then nearby, maybe even quite distant, masses would be influenced to move about slightly, and would absorb energy from your doing.  Is this considered gravitational waves?

Consider a binary system with the stars in circular orbits of radius r. Near to the system, say at distance R, and in the plane of the orbits, the effect would approximate the Newtonian law. When the stars are in line with the observer, the total force would be GM((R+r)-2+(R-r)-2) but when the are aligned orthogonal to the observer, that becomes 2GM(R2+r2)-1 hence there would be a local variation. However, that's not what is usually called gravitational waves, it is analogous to the "near field" behaviour of an antenna in EM. It would be a variation in the force towards the system hence a longitudinal wave. Far from the system, that falls as the inverse cube so becomes insignificant.

RS: If not what is it called, ...

I don't know if it has a name specifically but is too short range to be detectable. There remains a quadrupole component which propagates according to GR and that is what is known as gravitational waves.

RS: .. and was it accounted in the binary pulsar computation.

It isn't relevant to the Hulse and Taylor observations since they only measured the total orbital decay.

RS: And in either case, would gravitational wave detectors detect it?  (I'm thinking probably not because it is very low frequency and long wavelength).

Probably but only if we could get close enough. Going back to the original question and taking the second part first:

RS: .. can they be emitted by mutually rotating objects between which the distance doesn't vary (e.g. a spinning dumbbell)?

Yes they would be emitted by a "spinning dumbbell", in fact some people have even looked for GW emitted by "mountains" a few cm high on the surface of millisecond pulsars, anything that breaks the rotational symmetry is a potential source.

RS: Specifically, are they in or out of the plane of a scattering interaction (of which an orbit could be considered repeated scattering) ..

I'm a bit unsure of the polar diagram but I believe if you were to place a detector far from a binary system on the axis of rotation, there would be no waves to detect. The strongest amplitude would be in the plane of the orbits. That is what is illustrated by the linked animated gif from Wikipedia. It shows a perspective view of a square section of the orbital plane with the strength of the deformation shown perpendicular to the plane of the square. If you look at the front edge of that, it just goes up and down but if you look at the second URL (from  the same page), it shows that there would be a left-right deformation too. The third shows the same but for cross polarisation. The key point to note is that the waves are transverse, quite different to the "near field" Newtonian force variation.

The period of the waves would be half the orbital period of the binary system and the magnitude is very small, typically of the order of 10-23 as a fractional change for nearby binaries. The sensitivity of LIGO is shown in the last link but pay particular attention to the frequency range, the fastest binaries barely reach the mHz range, four orders of magnitude off the chart to the left!

p.s. The last link is just topical but has a nice animation of a GW (also linked). Imagine a detector measuring the width of the ellipse on the left.

https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:Wavy.gif

https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:GravitationalWave_PlusPolarization.gif

https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:GravitationalWave_CrossPolarization.gif

https://dcc.ligo.org/public/0006/G0900957/001/G090957-v1.jpg

http://www.esa.int/Our_Activities/Space_Science/LISA_Pathfinder_set_for_launch_site

http://www.esa.int/spaceinvideos/Videos/2015/09/Gravitational_waves

George,

Thanks for the links and your discussion.  I had seen all of these links except the last one.  However, the insight provided from your discussion was valuable.  I am familiar with near vs. far field effects in EM, and near field effects of gravity, and I was trying to discover the far field effects in gravity.

What I'm getting from your comment is that it is a transverse distortion of space, and there are complementary distortions on the two transverse axes.  There is no radial or time distortion.  Is that correct?

If so, if specifically there is no time distortion, then a light clock oriented, say, horizontally, would not change frequency as measured by any observer, even one far away and outside the influence of the wave.

For this to be true for local observers, the light must still travel locally at c, i.e. 30 million meters a second, or one meter in one 30 millionth of a second.  

It seems to me we would need reference points outside the influence of the wave and uninfluenced by it.  Then the total number of meters between those reference points would change as the wave passed, and an increased or decreased rate of this super-large light clock covering an inhomogeneous region of space could be detected.  If otherwise, please explain very specifically how the detector would work.

It also seems to me that even the above detector might not work.  If it has to be larger than the wave, it must surely be larger than a wavelength (though it is oriented transversely to the plane of the wave, not actually along a wavelength ... it just seems the wave would have to be at least as thick as a wavelength, probably several of them).  So the fast and slow regions would be encountered during the light transit and would average out.

RS: What I'm getting from your comment is that it is a transverse distortion of space, and there are complementary distortions on the two transverse axes. There is no radial or time distortion. Is that correct?

Yes, that's correct.

RS: If so, if specifically there is no time distortion, then a light clock oriented, say, horizontally, would not change frequency as measured by any observer, even one far away and outside the influence of the wave.

A light clock specifically bounces a photon across a known distance so behaves the same way as the LIGO interferometers. I would avoid that complication and just consider an atomic clock, the length of a second is defined by the energy levels of a single electron in the atoms so there is no distance involved, it is a local measurement of time at one point (or as near to that as QM allows). Since there is no time component in the wave, such a clock would be unaffected.

The light source for LIGO is source would also work at a fixed frequency. The interferometer layout sends wavefronts in two directions (multiple times I believe) and then compares their phase when they return to the start point. Different arm lengths mean different journey times so any variation can be detected. Think of the detector arms both in the plane of the wave, i.e. both transverse to the direction of propagation. When one arm is stretched, the other is compressed so the interference pattern moves by the phase shift.

RS: If it has to be larger than the wave, it must surely be larger than a wavelength (though it is oriented transversely to the plane of the wave, not actually along a wavelength ...

In the direction of the wave propagation, using HM Cancri as an example, the wavelength is 48 million km since the period is 160.75 seconds (half the orbital period). In the transverse direction, there are two cycles round the circumference of a circle centred on the binary system so the "wavelength" is many thousands of light years. Over the size of the Solar System, the compression/stretching is essentially constant at any given time in the plane of the wave.

RS: So the fast and slow regions would be encountered during the light transit and would average out.

The time for light to transit the interferometer from source to detector is small in comparison to the source period for binary systems. For faster waves, whole cycles would cancel out but any fraction of a cycle would be measured. That might be a limitation for LIGO but eLISA would work at much lower frequencies.

Hmm, well George, you are inadvertently convincing me that the waves may be undetectable.  

Recall that over scales of distance at which the spatial gradient can be ignored (seems safe that it can be ignored over meters or even kilometers, and maybe even tens of thousands of km), the light clock and atomic clock must agree.  Therefore "no time changes" means that the light signals will always move identically between two points embedded in the space-time which are not otherwise constrained.  

The only way we have of constraining points that I know of is through circumference which completely encloses a gravitational source, which hardly makes a practical detector.

It goes back to the principle of equivalence.  Gravitation is not detectable in a limited area.  For the low frequency waves, that is quite a large area.  I do not understand why there are no discussions of this in the various papers describing the detector schemes.

It is not a theoretical problem if the waves aren't practically detectable.  We still can accept them based on the combination of theory and notice of the emission energy losses.  It's just inconvenient.  It means we can't make much use of them.

RS: Therefore "no time changes" means that the light signals will always move identically between two points embedded in the space-time which are not otherwise constrained.

Yes, locally they move at speed c of course. However, if the end points of the light path are not constrained then the distance between them will vary as the wave passes. That is what is measurable.

RS: Gravitation is not detectable in a limited area.

Yes it is, an apple falls when released from a tree. Gravitation causes the distance between the apple and the bough to increase quadratically and we can easily measure that. Gravitational waves change the distance between the ends of the interferometer arms by a very small amount as a sine wave with respect to time. Measure that distance as the maxima and minima pass and you can detect the waves.

RS: I do not understand why there are no discussions of this in the various papers describing the detector schemes.

I don't understand why you think they would not be detected. Look again at the linked diagram (you've seen it before I know) and picture a ruler held in front of it, of course the reading will change. As long as the speed of light is c all along the ruler, using light travel time between the ends works just as well as long as the measurement time is small in comparison to the wave period.

LIGO at present is sensitive enough to detect HM Cancri, it is just swamped by terrestrial interference below 10Hz while the waves from Cancri are at 6.22mHz.

https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:GravitationalWave_PlusPolarization.gif

Hi George,

Such questions have caused debates between physicists who know more than me for nearly a century.  I'm not sure I'll be able to explain the problem in a post, nor do I know a single paper that is particularly clear about it. 

Tidal forces are detectable.  No question about that.  That includes changes of magnitude or direction of acceleration over some distance.

Uniform acceleration is not detectable.  It amounts to Rindler coordinates.  Since everything is accelerated the same amount no one notices.  Basically the same as the equivalence principle.

So there are two things at issue.  First is the relation of acceleration to the gravitational wave.  I am only fluent with static symmetric fields, but I assume there must be some acceleration.  Gradients in that acceleration are what you'd have to detect.  The distances themselves won't be detectable if there is no time dilation detectable, because time dilation is a direct measure of whether the relation between the velocity of light and a distance has remained the same or not.  If there is no time dilation and the distance changes, then the speed of light (in the coordinate sense, not local sense) has changed to match it.

Second is the wavelength, or size of the wave issue.  This relates directly to the gradient and whether tidal acceleration is detectable.  A sufficiently small piece of any gravitational field is uniform, and falls into the undetectable-because-uniform trap.

In the case of the apple falling from the tree, you have an anchor to the other side of the gravitational field, through the Earth, which you can use for reference.  If you had the tree on an unattached platform in free fall, you'd not notice an apple falling even if it came loose from the tree.

RS: ... I assume there must be some acceleration. Gradients in that acceleration are what you'd have to detect.

If an object moves with the location varying as a sine wave, obviously there are both velocity and acceleration as well as displacement, however current GW detectors are based on measuring the variation of displacement as a change in the distance between the ends of the legs so there's no point discussing acceleration. Velocity is zero when the displacement is a maximum.

RS: The distances themselves won't be detectable if there is no time dilation detectable, because time dilation is a direct measure of whether the relation between the velocity of light and a distance has remained the same or not.

No, it is a measure of the angle between the worldlines of two clocks, i.e. velocity. The speeds here are negligible and the detectors don't attempt to measure time dilation either. The easy way to think of this is to compare the effects of the wave when it is at maximum and minimum stretch. In both cases, the velocity of the ends is zero.

Simply, the speed of light along the path is c at those moments but the distance has changed so the interferometer will measure that as a time-of-flight change. That is the first order effect.

If you want to consider higher orders, when the distance is the mean, the velocity of the end points is highest. The speed of light is still c but the distance between the ends will vary while the light is traveling. You then have a variation of the ant-on-a-rubber-rope paradox only the length is varying very slowly and as a sine wave. The distance will still be measured to vary but perhaps with a small second order distortion. Given the miniscule strains involved, the distortion would be undetectable.

https://en.wikipedia.org/wiki/Ant_on_a_rubber_rope

George, re: "the distance between the ends will vary while the light is traveling."

Yes, this is the interesting thing, isn't it?  In fact, this is dependent on particular details of GR, and one could have gravitational radiation generally in, let's say a "class" of metric gravity theories, with variations among them in exactly what causes what, and therefore what the timing of various things are, and consequently the observables.

For example, you have a rod whose length will be determined ultimately by electromagnetic bonds.  The differential length of this rod will change at each point as the speed of light changes there.  Whether this is the result or cause of spatial changes would be immaterial.  Changes in the length of the rod would either not be observable, or if the change in the length of the rod "lags" for some reason, barely observable.  I call this a "bound" system because the EM bonds determine the length.

For my other example, you have a couple of objects floating in space, unbound.  As a wave passes, does the proper length between them remain the same like the rod?  Or does it vary because they have some sort of inertia relative to, let's call it their "coordinate" positions in space?  In that case the wave is easily measurable, even at low frequencies.

There is an analogous situation in special relativity.  If you accelerate a rod, lengths and vibrations of the molecules sync automatically to the new reference frame, as if Minkowski Space were a real tangible thing.

But if you accelerate two clocks on a bench, while the bench (bound) will contract, the clocks will not automatically adopt the new time and have to be manually synchronize.

And further, if you accelerate the clocks independently, even the length does not contract (like the Bell spaceship paradox).

So which kind of thing is a gravitational wave?  Particulars of the quality of spacetime and the degree to which the detector is bound to it by lightspeed might matter a lot.

I just saw this article, see the box "To catch a wave". I have to go out now but I'll try to respond to your post tomorrow.

http://www.nature.com/news/hunt-for-gravitational-waves-to-resume-after-massive-upgrade-1.18359?WT.ec_id=NEWSDAILY-20150915&spMailingID=49548807&spUserID=MTUwNTUzNDc0MzY4S0&spJobID=762064097&spReportId=NzYyMDY0MDk3S0

Thanks for the link.  The diagrams look exactly like a Michaelson-Morley interferometer.  I expect the same result for the same reason, to first order.

There could be second order effects, if the ends of the experiment do not stay solidly locked in the space-time.  To get first order effects, one would need a fixed coordinate reference, basically unobtainable I suspect without having a detector larger than the wave.

RS: ..  if the ends of the experiment do not stay solidly locked in the space-time

That's why the mirrors are suspended, they are not held in place so move with the distortion of spacetime. The distance between them therefore varies. The size of course is much less than the wavelength but the distortion is a factor which multiplies the length so  the longer the path, the better.

You've probably understood this already but I've drawn a sketch for my own benefit showing the effect of the waves in the plane of the orbits of a binary system. Compression and stretching are detectable but displacement isn't, it would move the entire Solar System by virtually the same amount. Another way to think of the compression/stretching aspect is that it is caused by the slight phase difference of the displacement effect at the two ends of the detector's optical path.

Going back to your last post, you said:

RS: For my other example, you have a couple of objects floating in space, unbound. ... Or does it vary because they have some sort of inertia relative to, let's call it their "coordinate" positions in space? In that case the wave is easily measurable, even at low frequencies.

Yes, that's exactly how it works. What holds each object at its location in spacetime is its inertia. An accelerometer attached to it would register nothing due to the equivalence principle as you mentioned before, so as long as the suspension doesn't damp out the motion, it will be detected.

Hi George,

Something has happened to my notifications from RG.  They moved to a secondary email, and then disappeared, so I just noticed your responses.

I have thought a lot about whether it makes a difference if the mirrors on an interferometer are suspended or attached in some way to guarantee the proper length between them.  This makes a big difference in SR when accelerating things.  If unattached, the proper lengths change rather than follow the Lorentz transform.  However, the acceleration afforded by the gravitational field may not have this problem?

In your second post - the figure is interesting by the way - you answered my dilemma above qualitatively, saying that they do in fact have inertia relative to their coordinate loci - not exactly the way you put it, but I think that's what it really is, because only coordinates define a position in space independently of the proper distances in the field.  So I'll tentatively accept that.  I would like to understand it better, but do not at the moment have a sufficient understanding of the way coordinates relate to the wave equation.

In fact, here is where I am.  I have the best understanding only of the static field, which of course can't radiate anything.  This question thread has been very useful, but what it (you) is/are telling me know is that I need to understand the field of at least a 2-object system, and how that field changes when they move.  I need this at a sort of elementary or pedagogical level.  Can you recommend anything?  I have maybe 7 or 8 GR books and several lecture notes on my computer, but none take a pedagogical approach.  Just sort of, here is the wave equation, figure it out. 

Everything I read says gravitational radiation can only be quadrupole, not dipole or monopole.  Do you not think that dipole radiation would have long ago been detected since it is much stronger?  Perhaps the gravitomagnetic theory (with which I'm passingly familiar) can be ruled out on this basis?

I am getting notifications but only on a work address and have been on holiday for the last two weeks. If I'm slow to respond in future, that may be the reason.

RS: ... because only coordinates define a position in space independently of the proper distances in the field.

Yes. If a force acts on a body, it's motion in local coordinates will include an acceleration term, if not it's motion is inertial or to put it another way, neglecting any constant velocity (which can be removed by a simple Lorentz boost), inertia causes the object to remain at the same coordinates. If the metric has a component that alters the proper distance between two such bodies, that change can be measured. The mirrors in the LIGO (etc.) interferometers serve that role hence the suspension is a crucial part of the equipment design.

RS: I need this at a sort of elementary or pedagogical level. Can you recommend anything? I have maybe 7 or 8 GR books ..

I have less resources than you and I am very much a beginner in this area but I had a look at some on-line material and the linked lecture notes seem to give an explanation of how to derive the wave solution. See if that helps.

http://webs.um.es/bussons/GW_lecture_KG.pdf

Thierry - i agree so far as the theory should be questioned, especially because grav waves should have been detected already.  I have reasons for not thinking gravitomagnetism is the answer, in fact I think the problem with GR is that it is contaminated with too many ideas from EM theory, and shortly I will write up something on this and if you like, send it to you for comment.

George - Thanks for the link, the picture of the train wreck with Einstein's equation has to have a significant subliminal message.  Or maybe not so subliminal.  :D

The concept of inertia when proper distances are not changing is new to me.  Is that what you are saying?  Is this a GR result?  If SO, then it undermines the philosophy of GR as it says really the underlying invariant loci, undetectable though they may be (like an ether) are what is important. 

ALL - I have reversed my earlier assent that grav waves demonstrate the conversion of gravitational energy to regular energy (EM, matter, etc.) and vice versa.  It is a subtle point, relating to questions about the theory, so follow closely...

1. A certain amount of energy and therefore mass is lost in one place, say a binary pulsar system.

2. At an unknown time later (speed of propagation is theoretical, not empirically established without detection), the same amount of energy-mass appears somewhere else.

In this 1-2 process there is at no time a change is the total non-grav and the total grav energy.  So there is no actual evidence of conversion from non-grav energy of the sending system to grav-wave energy and back to non-grav at the receiver.

You might think it is implied, but that is only with blind faith acceptance of existing theory.  Not actual measurement.  I'll give an example, and then propose rough measurement constraints.

Suppose gravity is due to position-momentum entanglement of mass-energy with other mass-energy in the universe.  Then when regular energy disappears in one place and appears in the other, it is from a QM perspective invalid to suppose either that it exists in some traveling state, or that there is a propagation "time" associated with it.  It is well known entanglement is not analyzable by relativity.  This happens to be the mechanism I favor.

How to measure so as to test true or false?

• If we detect waves and find the propagation is FTL, then forget gravitational energy, it doesn't really even exist,  Energy cannot "propagate" faster than light.  Some kind of entanglement is going on.
• Suppose there is the expected propagation delay.  That still does not prove the existence of gravitational energy.  It might be propagating as regular energy, vacuum energy, the vibration of space dust, etc.  One would have to develop some new kind of measurement to exclude all these possibilities, very difficult.

The problem with your questions is that, as you say, we currently don't have the technology to detect waves directly. In Newtonian theory, they could not exist, they are a prediction only of GR, so if GR is wrong, we don't even have a theoretical prediction for their existence. GR is quite definite, if it is correct then they would travel at the speed of light and if it is wrong, there is no reason to think they exist at all (though the Hulse & Taylor results would then need an alternative explanation).

A sensible approach would be to use known observations to develop an alternative gravitational theory first, and then ask if that theory predicts waves and if so if their character differs from those of GR.

A gravitational wave is supposed to be a displacement of space-time, so whatever event causes a gravitational wave must be an event that displaces space-time. Quite simple, really. A typical explosion in space does not displace space-time, it displaces only matter. Only the displacement of a fairly large amount of matter could cause a ripple in space-time.

The most effective means for causing a ripple in space-time would be the sudden disappearance of a large quantity of matter, and the space-time it occupies. The surrounding space-time would rush in at high speed and then rebound.

This appears to be the true mechanism of supernovas.  A star's mass becomes so dense with neutrons that it rips the fabric of space-time in a spherical shell around a star's neutron core causing a region of matter and space to completely unravel. The inward implosion then rebounds the outer layers of the star (mostly gases) into space with tremendous force while also causing a gravitational wave. The gravitational wave would occur before the visual supernova expansion.

The detection of the gravitational wave has to take place through a unit having more than the dimensions of space-time. For example, a change in certain types of rotating magnetic fields could serve as a tool for observing gravitational waves because its spatial-temporal dimensions is three dimensions of length (space) and two dimensions of frequency (resonance).

An interferometer can never detect a gravitational wave because all the components of the interferometer and all the units being measured are in units with space-time, or fewer, dimensions. The LIGO looking for gravitational waves is like someone in a flat screen world looking for spheres.

The magnetic structures that lead to solar x-ray flares on the Sun appear to have five-dimensional, space-resonance attributes. A systematic analysis of solar x-ray flares (during periods of increased solar magnetic activity) clearly show gravitational wave signatures on a near daily basis.

First I'll respond to David.  Re: "so dense with neutrons that it rips the fabric of space-time in a spherical shell..." - Anything with spherical symmetry seems unlikely to produce a wave in any theory.  It is definitely not a prediction of GR.  This is monopole radiation, it seems.  Not even dipolar is predicted for GR, only quadrupoler.

Re: "An interferometer can never detect a gravitational wave" - This was my going in position.  If as George said previously objects have inertia with respect to coordinate loci, not proper distances, then they would wiggle around, the proper distance would vary, and perhaps this could be detected.  George admits to not being a full expert.

Re: "detection of the gravitational wave has to take place through a unit having more than the dimensions of space-time. For example, a change in certain types of rotating magnetic fields" - This is an interesting idea.  I think that with the amount of money involved (there was a QA thread on here about whether these things are worth the expense) in solar satellite fleets, etc., the "experts" owe the public, especially the scientifically minded public, a better explanation of gravity generally and of how their detectors work in particular.  This hiding behind the obscurity of abstraction must stop.  This stuff is not nearly as complicate as QM or even electromagnetics, and there is no reason for not explaining it.

Now for George: "use known observations to develop an alternative gravitational theory first, and then ask if that theory predicts waves and if so if their character differs from those of GR" - Funny that you should ask, as I have done that.  However I predicted that gravity, being based on position-momentum entanglement, would result in entanglement-like propagation speeds, much faster than light and theoretically undetectable, certainly not usable for energy transfer.  That does not preclude the possibility that a system with a quadrupole moment would lose energy in the required way.  It just means I don't have a wave equation.  Even in the context of GR, based on what I know (not what an expert knows, which is why I asked this question) I'd predict if I had to right now that grav waves are undetectable with current and planned instrument designs.

Re Thierry: "Gravity is very comparable to electromagnetism" ... Sorry, my opinion stands.  I do not wish to argue.  I have spent a decade looking into this and was at first fascinated by gravitomagnetism, especially in regard to inertia but it doesn't work.

However a simpler reason can be shown with static fields.  Aside from being monopolar, the lines of force flux idea on which EM critically depends doesn't work with gravity.  Lines of force have to originate and terminate.  Without them EM doesn't work.  But gravity cannot be described this way.  The termination of a line of force implies shielding, which doesn't happen.  Gravitational attraction (space-time, whatever you want to call it) goes right through everything as if it wasn't there.

Robert - Just because a process begins as a spherical shell collapse does not mean the rebound will also be spherical. In fact, if the space-time was rushing to fill a void then the rebound could not be spherical as it would create another void. The resulting rebound wave would be a longitudinal wave with inverse spherical geometry (steradian). Also, the spherical collapse would likely occur in stages with three to five successive implosion events within a six to twenty four hour period. This would give us three to five longitudinal peaks of space-time compression with no transverse wave component.

As for gravity and magnetism, what if the mainstream idea of magnetism is wrong? What if there are two distinct types of charge in each electron and proton? We are familiar with the electric charge, but mainstream physics denies an inherent magnetic charge in the electron and proton. I provide the fundamental factors for calculating the magnetic charge from the conductance constant of space (which I show is actually reciprocal to the unit of magnetic flux and not reciprocal to resistance) and the inherent angular momentum of the subatomic particle.

In my work, I show that quantum magnetism should be directly proportional to the mass of a subatomic particle. In my work, the gravitational force is orthogonal to the magnetic force and the two are inseparable.

Thus a rotating magnetic field of the right design should react to a longitudinal gravitational displacement wave. In reality, the displacement wave has nothing to do with gravity, it is just proportional to the gravitational force and the real nature of the "gravitational wave" is that it is a longitudinal magnetic field (not transverse electromagnetic) displacement wave. This is another reason why rotating magnetic fields are required to detect "gravitational" waves. 

You are getting too far out for me.  Take one idea and find an experiment to prove or disprove it.  I've been working on one idea for 8 years now, and only just beginning to get a concept on how to experimentally test it.  Focus and persistence!

I have looked at the charts George suggested.  The next to last chart is interesting.  Perhaps lack of current detection means GW don't exist, OR perhaps it means coalescence of smallish objects and core collapse don't happen often or not in the range of sensitivity.

LISA looks like it has a better shot since it overlaps the binaries from which GW suspected decay matches theory.

You might see this in the news, my bet is on a false positive:

http://www.nature.com/news/has-giant-ligo-experiment-seen-gravitational-waves-1.18449

Re: relation of inertia and gravitomagnetism, see:  (this list does not imply that I agree or disagree with any of the positions taken)

• Ciufolini & Wheeler, 1st link below, "nothing would do more to demonstrate the inertia-influencing effect of mass in motion than to detect and measure the Einstein-Thirring-Lense-predicted gravitomagnetism of this rotating Earth."
• Nordtvedt's remarks on gravitomagnetism, 2nd link below, "Much has been written on the origin of inertia and Mach's principle in the past century, some of it outstandingly good. But there have only been a few jewels. Dennis Sciama's paper in the Monthly Notices of the Royal Astronomical Society back in 1953 is one. Another is Derek Raine's 1981 paper in Reports of Progress in Physics where he showed that Sciama's account of inertial reaction forces follows from general relativity theory in all isotropic cosmological models. And in the matter of the existence of gravitomagnetism, there is Ken Nordtvedt's 1988 paper in the International Journal of Theoretical Physics."
• http://www.relativitybook.com/resources/gravitomagnetism.html - "In relativity theory, gravitomagnetic effects are inertial or gravitational field effects that might be expected when there is relative motion between bodies. Some of these effects are currently included within standard "core" physics, some aren't. ... The name comes from an analogy with electromagnetism, where the motion of an "electric" charge produces "magnetic" side-effects. In gravitomagnetism, the "moving charge" is inertial-gravitational, and the "gravitomagnetic" effect can be considered as being due to a distortion of a body's surrounding inertial-gravitational field. These effects can be considered consequences of the finite speed of gravitational signals"
• Guilini, Inertia and Gravitomagnetism, 3rd link below.
• Particles already have mass-energy and therefore inertia, so they cannot cause it.  In QED, particles react through momentum exchange, for which they have to already have inertia.  The Higgs field is an energy field.  The Higgs Boson is very massive, i.e. has a lot of inertia.  It can certainly share that inertia by "sticking" to other particles, but it does not create or explain it.

Re: "Well, how do you interpret the magnetic part of gravity?"

• See above for conventional interpretations.  It is no longer something I follow closely.

Re: termination of lines of force, your comment: "Where do you see that with EM? If it doesn't happen with EM, it doesn't happen with gravity."

• You see it with attractive forces (like gravity) and only attractive forces.  See case 4 at the final link, and also the diagram.
• If you place an equal amount of positive charge around a negatively charged object, or vice versa, all the lines of force will terminate and at a distance no force will be felt. 
• Sounds like you might like to take a basic course in electricity.  There are tutors available at the 4th link.  I have two degrees in Electrical Engineering.
• Also, FYI, if you will use Google on the keywords in some statement or question you are presenting, you can just about answer it for yourself.  Even in areas where I know the answers well, I try to check and make sure I'm not misunderstanding or missing something important with a quick search before posting.  These discussions aren't personal to me, and have nothing to do with "what's in my head," although many posters (not just you) seem to take them that way.  I will only give a personal answer in a non-scientific discussion of my personal history, i.e. how I came to learn or understand something.  Otherwise, what I think or know is irrelevant.

https://books.google.com/books?id=UYIs1ndbi38C&pg=PA315&lpg=PA315&dq=inertia+and+gravitomagnetism&source=bl&ots=8m00RTi9q8&sig=g0FEhDxHViNbnqOZsJwsdiav_rs&hl=en&sa=X&ved=0CDcQ6AEwBGoVChMImef8kummyAIVCVyICh0GnABo#v=onepage&q=inertia%20and%20gravitomagnetism&f=false

http://physics.fullerton.edu/~jimw/general/inertia/nord.htm

https://www.itp.uni-hannover.de/~giulini/papers/Gravitomagnetism_Tait.pdf

http://www.tutorvista.com/content/physics/physics-iv/electric-charges/electric-field-lines.php

Thierry, I'm glad you enjoyed the links, but please do not ask me to respond to comments other people wrote. I just included enough words to show they had related the concept of gravitomagnetism and inertia in some way, that it wasn't just random usage of words in the same article, but I did not think about it (years ago I did, but not now).

Gravitomagnetism is used by numerous people and some of the uses are a little different.  If you are not using it in the majority way, I suggest you derive a new word. This diversity of usage was one of the problems with it.  Some people refer to early work by Heavyside et. al., for example, in which gravitational field equations are modeled on Maxwell.  Others like Ciufolini refer to mere analogies, i.e. the effects of motion of mass analogous to electric current in producing induced motion (frame dragging) in an unexpected direction, but not really in the direction that would follow from a literal interpretation such as Heavyside's.  So really the term itself has been corrupted.

I am working on light bending pedagogy, and alternate metric derivations, as far as my physics interests are concerned, and with a lot of other competing interests I don't have time to get back into gravitomagnetism or frame dragging.  I'm sure there are others on RG who will be happy to discuss.  Ask a question.  : )

The point you made about lines of force was very interesting.  I was selectively thinking only of attractive forces (and you apparently only of repulsive), and I'm glad you reminded me of other situations.  Attractive is what is appropriate, but I should keep the other in mind.  This affects the rationale for alternate metrics.

Robert, back in early September I said this which I'd like to correct:

GD: "I'm a bit unsure of the polar diagram but I believe if you were to place a detector far from a binary system on the axis of rotation, there would be no waves to detect. The strongest amplitude would be in the plane of the orbits.

That is incorrect, in fact the radiation towards the poles is stronger than in the orbital plane. Other than that, I believe the rest is correct.

Sorry this is a bit late but I'd rather flag up the error than leave you with disinformation.best regards

George

That's interesting, George.  In thinking about it just now, it seems reasonable.  That is where the "quadrupole moment" is easiest to visualize, from above the orbital plane.  But the figures typically do not show that.  The fuzziness in popular discussions and animations is why I started this thread.

I agree that most popular sites don't go into enough detail. Wikipedia is one where the equations are given but in discussing the Earth-Sun system, see the link. Note that the amplitude of the cross polarisation varies with inclination as cos(theta) which is 0 in the plane and 1 at the poles while the plus polarisation varies as (1+cos^2) so goes from 1 in the plane to 2 at the poles. Generally, popular sites illustrate the simpler plus-only variation in the plane. However, to understand the pattern anywhere other than in the plane, you would need to add those two components with the right phase. I expect the combination at the poles will be a simple rotation but I intend to do some work on that in a week or two when I get access to simulation software. If I achieve what I'm trying, I'll let you know.

https://en.wikipedia.org/wiki/Gravitational_wave#Wave_amplitudes_from_the_Earth.E2.80.93Sun_system