Paper: A causal mechanism for gravity

[MigL]

I find it quite annoying that you can criticise the speck in the mods' eyes; they are human after all, and we all have some biases.
Yet you refuse to cknowledge the tree trunk in your eyes, that stubbornly refuses to follow rules for discussion, present evidence to support your position, and acknowledge evidence presented against your conjecture, evidence  which supports current accepted theories.

There used to be an old saying along those liines.
I think you'll find it in Matthew 7.5 in the King James version of the Bible.

[Phi for All]

5 minutes ago, MigL said:

There used to be an old saying along those liines.
I think you'll find it in Matthew 7.5 in the King James version of the Bible.

Beware of false prophets who question Relativity? 

[joigus]

52 minutes ago, MigL said:

I find it quite annoying that you can criticise the speck in the mods' eyes; they are human after all, and we all have some biases.
Yet you refuse to cknowledge the tree trunk in your eyes, that stubbornly refuses to follow rules for discussion, present evidence to support your position, and acknowledge evidence presented against your conjecture, evidence  which supports current accepted theories.

There used to be an old saying along those liines.
I think you'll find it in Matthew 7.5 in the King James version of the Bible.

Thou shalt not bear false hypothesis?

[rjbeery]

I've re-written this paper completely. Simplified for easier understanding, added diagram, bibliography, exported as PDF to make the look consistent. Looking for feedback. Thanks in advance!

 

https://drive.google.com/file/d/1KsfgRHJvIYfm45NcJCKg6fGalDxp3QMJ/view?usp=sharing

[swansont]

The ability to predict gravitational effects on light by applying Snell's Law to the graded time dilation field surrounding a massive object does not mean the implication is that all gravitational effects are purely the result of time dilation. (I lifted this from your redundant thread; the rules ray that one must be able to participate without clicking any links, as you should now know)

Time dilation is the result of GR, as are effects on light. It's not unreasonable to think that you could parameterize and/or recombine the equations to cast the effects on light in terms of time dilation.

If you want to show something is causal, you need to isolate it from other possible causal effects. i.e. show that there are effects on light where time dilation occurs but where gravity is absent, or where you have a constant gravitational potential.

Does light bend in a rapidly moving reference frame at constant velocity, where time dilation would be easily noticeable?

 

[rjbeery]

2 hours ago, swansont said:

The ability to predict gravitational effects on light by applying Snell's Law to the graded time dilation field surrounding a massive object does not mean the implication is that all gravitational effects are purely the result of time dilation

Agreed, which is why I include this in the summary:

Quote

Parsimony and equivalence suggest that this mechanism is sufficient to explain gravitational forces on massive objects as well (possibly in one of the forms of EM mass in the literature [Bha07] [Wil97]).

If we can account for gravitational effects on light with time dilation, with a plausible reason to expect the same effects on massive objects, then it's bizarre to believe that there must be some additional mechanism (that is both identical and redundant to the time dilation effects), IMO.

 

2 hours ago, swansont said:

If you want to show something is causal, you need to isolate it from other possible causal effects.

I don't need to do that in this case. Snell's Law completely and perfectly describes the gravitational behavior of light. To suggest that there might be other possible causal effects on the light would mean that we're breaking the laws of optics as we know them.

[Markus Hanke]

Suppose you have a rotating massive body of some kind. Further suppose you have two identical rays of light that pass this body in the equatorial plane, such that one passes along the central body’s direction of rotation, while the other one passes opposite its direction of rotation. The light rays are identical in all other aspects, ie they pass the rotating body at the same distance.

GR predicts that these light rays are frequency-shifted by slightly different amounts as they pass the body, even though they both pass at the same distance, and in the same equatorial plane.

Alternatively, you can put two sensitive clocks in the same orbit around the rotating body, but let them move in opposite directions. After one orbital period, even though they will have traversed the exact same region of space on the exact same orbit, their clocks will have recorded slightly different times.

How do you explain these using Snell’s Law, and a single scalar field, respectively? 

I have said it many many times on here before - you can not describe all degrees of freedom of gravity using either scalar or vector fields alone, or any combination of these, for fundamental reasons. You need at least a rank-2 tensor field. 

[rjbeery]

1 hour ago, Markus Hanke said:

How do you explain these using Snell’s Law, and a single scalar field, respectively?

The gradient of the field is what curves the light ray, so scalars are not enough. I'll give your scenario some thought. In the meantime, perhaps you could look over the mathematics of the paper for errors (rather than the conclusion)?

[Markus Hanke]

7 minutes ago, rjbeery said:

In the meantime, perhaps you could look over the mathematics of the paper for errors (rather than the conclusion)?

The problem isn’t the mathematics, but the basic premise - namely that you assume the existence of the notion of ‘gravitational potential’, as a generally applicable concept. If such a potential exists, then the following boundary conditions must apply:

1. The spacetime is asymptotically flat

2. It is spherically symmetric

3. It is stationary

4. It is static

And vice versa - if any of these conditions do not hold, you cannot meaningfully define a gravitationally potential in a self-consistent way. This is basically to say that the work done to get from one point in a gravitational field to another must not depend on which path you take through spacetime, or else the difference between these points can’t be consistently described by a single number.

You are right in one respect - if, and only if, you are in a spacetime that admits a consistent definition of gravitational potential, then you can describe gravitational light deflection as a refraction-like process, analogous to some variation of Snell’s Law. An example would be any system that can approximately be described as Schwarzschild. 

The issue is that it doesn’t generalise; violate any of the above conditions, and it will no longer work. A rotating body is the simplest example. So what I am saying is not that you are categorically wrong; it’s just that your formalism works only for a small subset of gravitational scenarios. It is not a general description of gravitational degrees of freedom. But for some special cases, I grant you that such an approach may come in handy.

Two more examples to illustrate the point; each of these violates one or more of the above conditions:

1. In free space far from other sources, emit two parallel rays of light in the same direction - despite the energy-momentum they carry, they remain parallel and don’t gravitationally deviate. Now repeat the experiment, but emit the same parallel rays in opposite directions - they now gravitationally converge! (This is an example of a pp-wave spacetime)

2. Consider two intersecting beams of light at right angles, but in the same plane (a gravitational wave detector). Now expose this setup to a gravitational wave front - as the wave passes, the relative lengths of the beams will contract and expand relative to one another, even though their distance to the source (which is very far away!) is identical. Furthermore, comparing two or more such setups at different orientations in space (ie at different points on Earth) reveals the nature of these waves to be quadrupole, with two polarisation states at 45 degree angles - which necessarily implies that the field must couple to a rank-2 tensor. This is why gravity needs at least a rank-2 tensor description.

I could give more examples where the gravitational potential approach doesn’t work, but I think you can see my point - ‘gravitational potential’ can only be meaningfully defined under certain conditions, it is not a general concept.

[SergUpstart]

4 hours ago, Markus Hanke said:

I could give more examples where the gravitational potential approach doesn’t work, but I think you can see my point - ‘gravitational potential’ can only be meaningfully defined under certain conditions, it is not a general concept.

What about the 4-potential? It is included in S. Fedosin's theory of gravity

http://sergf.ru/ktgen.htm

[swansont]

13 hours ago, rjbeery said:

I don't need to do that in this case.

Well, I disagree, but in any event you need to address objections to your idea. You can’t ignore the fact that your claim that time dilation causes optical deflection fails in the situation I described, which falsifies the hypothesis that it’s caused by time dilation.

 

[rjbeery]

14 hours ago, Markus Hanke said:

If such a potential exists, then the following boundary conditions must apply:

1. The spacetime is asymptotically flat

2. It is spherically symmetric

3. It is stationary

4. It is static

Why do you say this? Why would gravitational potential require those boundary conditions?

Off-the-cuff, I would say that movement in a direction opposite of a rotating body increases the corresponding relativistic masses of the respective objects. Increased time dilation should be expected.

I believe what you're submitting is that, even if the potential/refraction connection is correct, that gravitational potential cannot accurately describe expected gravitational movement in GR. Is that right?

[rjbeery]

12 hours ago, swansont said:

Well, I disagree, but in any event you need to address objections to your idea.

I'm not exactly sure what your objection is.

On 2/10/2022 at 10:57 AM, swansont said:

If you want to show something is causal, you need to isolate it from other possible causal effects. i.e. show that there are effects on light where time dilation occurs but where gravity is absent, or where you have a constant gravitational potential.

If this is it, then we take a glass of water in deep space (i.e. constant gravitational potential of zero) and stick a straw in it; the straw will appear to bend, and it's due to a reduction in the velocity of light in water.

 

[swansont]

1 hour ago, rjbeery said:

If this is it, then we take a glass of water in deep space (i.e. constant gravitational potential of zero) and stick a straw in it; the straw will appear to bend, and it's due to a reduction in the velocity of light in water.

And how is that caused by time dilation?

[rjbeery]

17 hours ago, swansont said:

And how is that caused by time dilation?

It's time dilation caused by a change in the velocity of electromagnetic waves as measured by the index of refraction. Whether that cause is due to an abrupt change in the medium of travel, like vacuum-to-water, or if it's due to a gradual change in the medium of travel, like space-time approaching a large mass, is irrelevant. The math and behavior, both theoretical and in practice, are equal in both scenarios...and the presence of gravitational potential is not required. In other words, the change in velocity is (apparently) necessary and surely sufficient to display gravitational behavior.

[swansont]

26 minutes ago, rjbeery said:

It's time dilation caused by a change in the velocity of electromagnetic waves as measured by the index of refraction. Whether that cause is due to an abrupt change in the medium of travel, like vacuum-to-water, or if it's due to a gradual change in the medium of travel, like space-time approaching a large mass, is irrelevant. The math and behavior, both theoretical and in practice, are equal in both scenarios...and the presence of gravitational potential is not required. In other words, the change in velocity is (apparently) necessary and surely sufficient to display gravitational behavior.

You said time dilation causes the refraction and now you’re saying it’s the other way. And without actually showing where time dilation is involved.

[Markus Hanke]

On 2/11/2022 at 3:24 PM, SergUpstart said:

What about the 4-potential?

If the source of the field were a 4-potential (or any combination of vector+scalar potentials), then gravitational radiation would have polarisation states offset by a 90 degree angle - just like electromagnetism. This is not the case though, as in reality the two polarisation states are offset by 45 degrees, meaning such radiation fields can only couple to rank-2 tensors as source.

On 2/12/2022 at 1:34 AM, rjbeery said:

Why do you say this? Why would gravitational potential require those boundary conditions?

I have mentioned this further down - because the work done to go between points in the field must be independent of the path taken, or else the difference between those points cannot be a single unique quantity (=potential). This is how gravitational potential energy is defined - as a path integral between points within the field. If the value of this integral explicitly depends on the path, the definition becomes meaningless. This is true also in Newtonian theory.

The potential must also vanish at infinity, or else you are left with a degree of freedom that cannot be fixed from the theory. Taken together, that gives you the symmetry requirements I mentioned. 

On 2/12/2022 at 1:34 AM, rjbeery said:

Off-the-cuff, I would say that movement in a direction opposite of a rotating body increases the corresponding relativistic masses of the respective objects. Increased time dilation should be expected.

Why would it do that? The distance to the central body is the same, so your gravitational potential would be the same.

Also, relativistic mass is not a source of gravitational time dilation.

On 2/12/2022 at 1:34 AM, rjbeery said:

I believe what you're submitting is that, even if the potential/refraction connection is correct, that gravitational potential cannot accurately describe expected gravitational movement in GR. Is that right?

No, what I am saying is that your refraction model only works in a subset of particular spacetimes with particular symmetries. It cannot be generalised to describe all gravitational degrees of freedom, as GR does. So it’s not wrong as such, just limited. 

8 hours ago, rjbeery said:

and the presence of gravitational potential is not required

I’m afraid I lost you now - I thought your entire idea is based on the concept of a gravitational potential? If no such thing is required, and you don’t accept GR (ie no curvature), then what is it about spacetime that yields your refractive index?

8 hours ago, rjbeery said:

The math and behavior, both theoretical and in practice, are equal in both scenarios

Hm...Im not so sure. How would you show this mathematically?

On 2/10/2022 at 3:54 AM, rjbeery said:

I've re-written this paper completely.

On a very general note, I’m curious - why do you feel the need to replace GR in this way? It works perfectly well as it stands, and we have already known for a long time that relativistic gravity cannot be a scalar or vector theory, or any combination thereof (ref Misner/Thorne/Wheeler). I also don’t see how your idea would locally yield Special Relativity.

Edited February 13, 2022 by Markus Hanke

[rjbeery]

8 hours ago, swansont said:

You said time dilation causes the refraction and now you’re saying it’s the other way. And without actually showing where time dilation is involved.

Poorly worded. The change in the velocity of light is caused by a change in the index of refraction of the traversed medium. A slowing of light is the very definition of time dilation. Did you read my paper? Because you made a vague remark implying that you did not.

[beecee]

1 hour ago, rjbeery said:

Poorly worded. The change in the velocity of light is caused by a change in the index of refraction of the traversed medium. A slowing of light is the very definition of time dilation. Did you read my paper? Because you made a vague remark implying that you did not.

Excuse my interruption, I'm pretty sure swansont can answer better then I, but the speed of light, "c" is constant. In simple lay person's language, light appears to slow down, but simply has longer paths to travel. With reference to "the index of refraction" is another kettle of fish. Photons are absorbed and reemmited, and that process I believe can also be understood as having longer paths to travel.

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

In physics and relativity, time dilation is the difference in the elapsed time as measured by two clocks. It is either due to a relative velocity between them (special relativistic "kinetic" time dilation) or to a difference in gravitational potential between their locations (general relativistic gravitational time dilation).

And the index of refraction is...... 

"The index of refraction, n, is the ratio of the speed of light in a vacuum, c, to the speed of light in a medium, c':

One consequence of this difference in speed is that when light goes from one medium to another at an angle, the propagation vector in the new medium has a different angle with respect to the normal".

https://spie.org/publications/fg08_p13_index_of_refraction?SSO=1#:~:text=The index of refraction%2C n,with respect to the normal.

ps: I remember well another suggesting, actually demanding that  Carver Mead's G4v vector gravity theory, and  a so called improvement by some bloke called Svidzinsky? that also questioned along with the validity of GR, the existence of BH's despite all the discoveries by aLIGO. 

Any potential discovery, and/or improvement of GR will of course also need to run the gauntlet, so to speak, and not only predict and align with what GR says, but also add new observational verifications that GR does not.

OK, I now hand over the operational status of this thread back to the experts.

 

 

Edited February 13, 2022 by beecee

[SergUpstart]

5 hours ago, beecee said:

"The index of refraction, n, is the ratio of the speed of light in a vacuum, c, to the speed of light in a medium, c':

In fact, the relative refractive index is not the ratio of the speeds of light, but the ratio of wavelengths. Just at a constant frequency, it is equal to the ratio of the speeds of light, but more generally, if the frequency changes, then this is not the case.

[swansont]

6 hours ago, rjbeery said:

A slowing of light is the very definition of time dilation.

No, it’s not. This is something you made up.

6 hours ago, rjbeery said:

Did you read my paper? Because you made a vague remark implying that you did not.

Did you ever read rule 2.7? This suggests you have not.

members should be able to participate in the discussion without clicking any links or watching any videos. … Attached documents should be for support material only; material for discussion must be posted

[SergUpstart]

10 hours ago, Markus Hanke said:

This is not the case though, as in reality the two polarisation states are offset by 45 degrees, meaning such radiation fields can only couple to rank-2 tensors as source.

Are these 45 degrees visible in the experiment or is it just a theory?

 

If any vector is in a plane oriented at an angle of 45 degrees to the direction of wave propagation, then it can be decomposed into longitudinal and transverse (at 90 degrees) components that are modulo equal to each other, is that so?

Edited February 13, 2022 by SergUpstart

[rjbeery]

14 hours ago, Markus Hanke said:

I have mentioned this further down - because the work done to go between points in the field must be independent of the path taken, or else the difference between those points cannot be a single unique quantity (=potential). This is how gravitational potential energy is defined - as a path integral between points within the field. If the value of this integral explicitly depends on the path, the definition becomes meaningless. This is true also in Newtonian theory.

Gravitational potential isn't even at the heart of anything here. For the falling body, A, I'm using PE + KE = constant as a shortcut to determine the free-fall kinetic energy as a function of r. The shell velocity could be determined in other ways. As for the light ray, B, I never refer to gravitational potential at all. GR time dilation is what determines the geodesic. Surely you'll agree that the GR time dilation field, as determined by an observer, is in fact a differentiable field?

 

12 hours ago, beecee said:

Any potential discovery, and/or improvement of GR will of course also need to run the gauntlet, so to speak, and not only predict and align with what GR says, but also add new observational verifications that GR does not.

I'm not refuting GR in any way. I'm showing a mathematical analogy between two disparate fields (gravity and optics) and suggesting that they are literally the same thing. This doesn't change any predictions made by GR, but it certainly could simplify mathematical treatments in it.

 

6 hours ago, swansont said:

members should be able to participate in the discussion without clicking any links or watching any videos. … Attached documents should be for support material only; material for discussion must be posted

I'm not sure why you would want to discuss a paper, or even raise objections to it, if you won't read it. That seems a bit combative to me. Nevertheless, the entire concept can be summarized in the following diagram.

[swansont]

3 hours ago, rjbeery said:

I'm not sure why you would want to discuss a paper, or even raise objections to it, if you won't read it. That seems a bit combative to me.

It’s a matter of getting you to follow the rules. Refusing to do so seems combative to me.

 

3 hours ago, rjbeery said:

Nevertheless, the entire concept can be summarized in the following diagram.

I don’t see how this relates to time dilation causing anything.

[rjbeery]

1 hour ago, swansont said:

I don’t see how this relates to time dilation causing anything.

The light ray, B, isn't bending due to gravitational effects; it's bending due to the refraction index being set to the time dilation function. See "n = gamma" in the corner? B is approaching the mass M purely through optical considerations.

 

On 2/10/2022 at 8:15 PM, Markus Hanke said:

Suppose you have a rotating massive body of some kind. Further suppose you have two identical rays of light that pass this body in the equatorial plane, such that one passes along the central body’s direction of rotation, while the other one passes opposite its direction of rotation. The light rays are identical in all other aspects, ie they pass the rotating body at the same distance.

I gave this some thought. My response is that the gravitational potential may be the same for each ray, and the time dilation may be different, but it's the gradient that determines the optical path of each. We'd need a scenario where light rays take similar paths but move through different radial gradients.