Gravity speed vs light speed experiment

[1bobwhite]

DaleSpam,

Then I guess the goal is to develop the apparatus and methods to make second-order experiments, correct?

You say my proposed experiment is a first-order one. How so?

Regards,
Bob.

 

[Russell E]

DaleSpam,

Then I guess the goal is to develop the apparatus and methods to make second-order experiments, correct?

You say my proposed experiment is a first-order one. How so?

Regards,
Bob.

For electromagnetism, the aberration effect is second-order, but for gravitation (according to general relativity) it is actually fourth order, so this isn't a very practical way of trying to infer a propagation speed.

I get the impression that you haven't really grasped what people are saying. Your "proposal" is to check whether the direction of the Sun's gravitational pull points in the same direction as the Sun's optical rays as viewed from the Earth, or whether the directions differ by the amount of aberration that we know applies to the Sun's light. The answer to this is already well known, and has been known for over two centuries (see Laplace), and is explained in the very article that you linked. The answer is that, just as in the case of electromagnetism, the force between two "charges" (or masses) does not exhibit aberration to the first order. The "order" refers to the exponent on (v/c). For example, if the expected aberration angle was first order, it would be proportional to (v/c), whereas if it is second order it would be proportional to (v/c)^2, and for fourth order it would be proportional to (v/c)^4. The quantity v is the speed of the moving masses or charges. The aberration angle for light is first order, but for the force of gravity (according to general relativity, with a propagation speed of c) it is fourth order. So, hopefully you can see that there is no hope of detecting such a small amount of aberration.

Moreover, this doesn't really address what I suspect is your underlying agenda. You aren't trying to check the predictions of general relativity (which unambiguously entails a propagation speed of c for gravity), you are trying to find evidence that general relativity is wrong. The point is, checking aberration angles isn't going to prove relativity wrong, because relativity predicts an aberration angle proportional to (v/c)^4, which is experimentally indistinguishable from zero. The lack of measurable aberration represents confirmation (not falsification) of general relativity - but this is presumably the exact opposite of your intention. So you need to think of something else.

 

[1bobwhite]

Russell E,

Nearly all of the responses to this experiment have apparently been made from theory only, and with an irritation that an attempt is being made at possibly showing that the GR theory may be in need of reconsideration.

Well my "agenda" is to try to establish a repeatable demonstration of the real world forces that can be compared to the theoretical assertions.

Whether the results confirm or refute the supposed facts of these theories will have to be determined after the data is in. My attempt is to try to set up the methods, apparatus, and controls that can accurately measure these forces within the constraints of the experiment, and have them repeatable and verifiable by the Professionals.

Many of my references and reasons for making the attempt at the experiment are contained in the following article: http://iopscience.iop.org/0004-637X/590/2/683/fulltext

Excerpt: "We calculate the delay in the propagation of a light signal past a massive body that moves with speed v, under the assumption that the speed of propagation of the gravitational interaction cg differs from that of light."

This is the first sentence of the article.

Excerpt: " We conclude that recent measurements of the propagation of radio signals past Jupiter are sensitive to (alpha)1 but are not directly sensitive to the speed of propagation of gravity.

This is the ending sentence of the same paragraph.

Excerpt: "We thus conclude that the v/c corrections to the Shapiro time delay are normal 1.5 PN corrections that occur when there are moving bodies but that they have nothing to do with the speed of propagation of gravity, insofar as it affects the retardation of gravitational interactions."

Excerpt: "Therefore, measurements of the propagation of radio waves past Jupiter do not directly constrain the propagation speed of the gravitational interaction."

The next section of the article goes into the math to show their position.

Excerpt:
1 A similar conclusion was reached by Carlip (2000) in the context of binary motion, in response to a proposed bound on the speed of gravity by Van Flandern (1998).

A foot note to show that Van Flandern's proposal was being considered with recognition for his work, that has been referred to here as "crackpot".

Excerpt: "We have shown that the speed of propagation of gravity has no direct influence on the time delay of light to 1.5 PN order. The only effect comes from any modification of the PPN parameters that might arise in a theory with a different propagation speed. This contradicts claims made by Kopeikin (2001, 2002)."

Followed by more references to theories and time frame references that support their conclusions.

All I have heard on this forum so far is the negatives of how wrong I am in my thinking and how impossible and worthless the experiment is.

Not one single post has been made for how to design a workable experiment or how to improve a procedure to make extremely sensitive measurements.

By the previous referenced article you can see that this issue has not been settled and is still open for speculation, theory making, and experimentation.

I realize this an amateur forum for amateurs to discuss science, but in history it has been the amateurs that have made many significant contributions to the discoveries of science.

Why are there so few amateurs taking up this challenge?

Bob.

 

[ZikZak]

Russell E,

Nearly all of the responses to this experiment have apparently been made from theory only, and with an irritation that an attempt is being made at possibly showing that the GR theory may be in need of reconsideration.

Well my "agenda" is to try to establish a repeatable demonstration of the real world forces that can be compared to the theoretical assertions.

In order to test "theoretical assertions," you are obligated to know what those assertions are. What people are telling you is that your characterization of those theoretical assertions is wrong and your proposed experiment does not test them the way you think it does.

This is the experiment I'm proposing:

Use gravity sensors of the highest sensitivity to determine the "peak" of solar gravitational pull in the vertical direction, and compare this peak time with the peak of solar radiance that occurs at noon.

If the peaks are coincidental, then the speeds are the same. If there is a lag of eight minutes of the peak of solar radiance, then gravity is not light speed limited.

If I may summarize: you want to measure the direction of the solar force due to gravity and determine whether that direction is in the direction of the apparent (aberrated, retarded) position rather than the actual position of the sun, and if so, then declare that the speed of gravity is c. On the other hand, if the direction of solar gravity is in the direction of the actual sun, you will declare that the speed of gravity is infinite and GR is wrong.

But you are WRONG ABOUT WHAT GR PREDICTS. Life is more complicated than you make it out to be. GR *actually* predicts: (1) gravitational influences travel at c, AND (2) that the measured force will be in the direction of the REAL sun, not the apparent sun. You are complaining about people making only theoretical objections to your experiment, but that is because you have *misstated the theory* to begin with. You intend to use a result predicted by GR to claim GR is false. That is not allowed.

You could do the same experiment supposing that the sun were electrically charged, and you would measure that the direction of the electric attraction/repulsion is towards/away from the REAL sun, not the apparent sun. From this, YOU would conclude that the speed of electromagnetism must be infinite, which is a contradiction to your initial assumption that its speed is c (thus abberating the sun's position in the first place). But physicists looking at this experiment would know that the reason the attraction is towards the real sun is that the combined effects of electricity and magnetism conspire to make it (almost exactly) that way and the flaw was yours, not the theory's, for making an invalid deduction and ignoring magnetism. This experiment is conducted all the time in the lab. A similar phenomenon happens with gravity.

In any case, here is an experiment: observe the orbit of the Earth to determine if it is an ellipse. If so, then the solar force of gravity MUST be towards the real, not abberated sun, because ONLY central 1/r^2 forces generate closed elliptical orbits. Any noncentral force results in a rosette, not an ellipse. Since the Earth's orbit is elliptical (once effects of other planets, etc. are removed) then the force must indeed be central, directed towards the real, not abberated, sun, thereby confirming the predictions of GR.

 

[Dale]

Then I guess the goal is to develop the apparatus and methods to make second-order experiments, correct?

Yes, that is the purpose of LIGO and LISA
http://www.ligo.caltech.edu/
http://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna

You say my proposed experiment is a first-order one. How so?

I mean if you take the equation (equations 9 and 10) for the gravitational field experienced here on Earth as a function of, v, the speed of the sun (relative to our detector) and do a Taylor series expansion in powers of v then you will find that your peak of the day is associated with the first term. The speed of gravity is not.

 

[Russell E]

Nearly all of the responses to this experiment have apparently been made from theory only, and with an irritation that an attempt is being made at possibly showing that the GR theory may be in need of reconsideration.

That doesn't describe any of the response that I've seen. I think you've mis-read and/or mis-interpreted the responses.

Well my "agenda" is to try to establish a repeatable demonstration of the real world forces that can be compared to the theoretical assertions.

You've missed the points that have been made. First, the thing you say you are trying to demonstrate was already demonstrated over 200 years ago by Laplace, when he showed that the stability of the planetary orbits imply virtually no aberration in the force of gravity. This is a well-known fact. Second, the results of this demonstration have already been "compared to the theoretical assertions". In particular, the absence of discernable aberration is consistent with the only empirically viable theories of gravity that we possess, in which the propagation speed if c. There is no known empirically viable theory of gravity in which the propagation speed differs from c, which is one of the things that makes it so difficult and contentious when trying to design experiments to test for the speed being different from c. But for the purposes of this thread, all of that is irrelevant, because the one thing we know for sure is that the proposal you are discussing, to infer the speed of propagation from simple force aberration, is untenable.

Whether the results confirm or refute the supposed facts of these theories will have to be determined after the data is in.

Again, you've missed the point. The data you're discussing is already "in". It's been "in" for over 200 years. And the theoretical implications of this particular bit of data are well understood (by physicists).

Many of my references and reasons for making the attempt at the experiment are contained in the following article: http://iopscience.iop.org/0004-637X/590/2/683/fulltext

All the excerpts you quoted from that reference simply confirm what people here have been telling you. None of those proposed observations are of the kind that you are discussing. You are talking about measuring the direction of the force, i.e., simple force aberration, which is already well known. There is no appreciable aberration in any relativistic force, and this applies to electromagnetism as well as gravity and the strong and weak nuclear forces.

Excerpt: 1 A similar conclusion was reached by Carlip (2000) in the context of binary motion, in esponse to a proposed bound on the speed of gravity by Van Flandern (1998).

A foot note to show that Van Flandern's proposal was being considered with recognition for his work, that has been referred to here as "crackpot".

Again, the excerpt you quoted simply confirms what people have been telling you. Van Flandern was indeed a crackpot, as can be inferred from the excerpt that you quoted. He made the same elementary mistake that you are making, i.e., he supposed that the absence of aberration in the force implies a Laplacian lower bound on the propagation speed. The is a well known fallacy for over a century, and was even described as a fallacy in the paper that Van Flandern cited as his source.

All I have heard on this forum so far is the negatives of how wrong I am in my thinking and how impossible and worthless the experiment is.

Your thinking IS wrong. As to the experiment, it isn't so much that it's worthless or impossible, it's just redundant. The absence of gravitational aberration has been a well established empirical fact for centuries.

Not one single post has been made for how to design a workable experiment or how to improve a procedure to make extremely sensitive measurements.

That's simply not true. Many people have pointed out the most sensitive way of determining the aberration of the gravitational force, namely, by observing the orbital stability of the planets, from which we can say that there is no discernable (first order) aberration in the force of gravity. And of course this is entirely consistent with general relativity and with a propagation speed of c.

Why are there so few amateurs taking up this challenge?

I think you underestimate the intelligence of most amateurs, who are fully capable of grasping that the absence of aberration in the force of gravity is (1) perfectly well established by observation, and (2) perfectly consistent with general relativity and a propagation speed of c.

 

[1bobwhite]

Russell E,

Thank you for your point by point explanation. But just a few more questions though.

Does the article : http://iopscience.iop.org/0004-637X/590/2/683/fulltext agree with or disagree with the Fomalont and Kopeikin experiment?

If there in no apparent aberration in the gravity force in the solar system even at the extreme distances of Uranus and Neptune, how is that consistent with the speed of light that has such a time delay at those distances?

If there is a propagation speed of gravity, what is it?

Finally, I have full faith in the efforts of our amateur community, and in no way am I underestimating their intelligence.

Thank you DaleSpam, for your answer.

Bob.

 

[Dale]

If there in no apparent aberration in the gravity force in the solar system even at the extreme distances of Uranus and Neptune, how is that consistent with the speed of light that has such a time delay at those distances?

The time delay to Neptune is nothing compared to the age of the sun.

Maybe this analogy will help. Let's say that you have a metal plate that you can push down on. If you push on it briefly you will get a ripple which goes outward at the speed of sound in the plate. However, if you push and hold it you will get a momentary ripple followed by a static deformation. Measurements of the static deformation, such as the direction of the path of steepest descent, will tell you nothing about the speed of sound in the metal.

Similarly, suppose that you were to charge up a sphere with an electrostatic charge. Measurements of the static e-field cannot give you any information about the speed of light.

In this case, the gravitational field of the sun has been essentially static for eons. Measurements of it will not give you information about the speed of gravity.

Do you see the similarity in these situations and understand why none of them provide any information about the characteristic wave speed?

 

[1bobwhite]

DaleSpam,
Your analogies are good, but they also show the possibilities for further experimentation.
For instance, let's say gravity between the sun and the Earth is static as you say and under tension and distorted, it is nevertheless still a continuous connection between the two bodies. As with the steel plate or a drum head that is under stress distortion, any further momentary distortion or "ripple" will proceed from the source and radiate through the material at the speed of that materials propagation rate.

The search for gravity waves is a search for these ripples. And although the proposed experiment misses the point as you have said, the search for the ripples may also be directed to the noise and unexplained gravity signals of the sensitive gravimeters that will be used in the experiment.
The next logical step would be to learn how to induce the ripples so that the experiments already in place could detect them. But that is for another forum.

 

[Dale]

any further momentary distortion or "ripple" will proceed from the source and radiate through the material at the speed of that materials propagation rate.

The search for gravity waves is a search for these ripples.

Exactly, yes.