Gravity speed vs light speed experiment

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Is this a valid experiment for testing gravity speed.

  • Are gravimeters sensitive enough?

    Votes: 1 100.0%
  • Can a gravity peak be determined?

    Votes: 0 0.0%
  • Can extrapolation methods be accurate?

    Votes: 0 0.0%
  • Has this experiment been done before?

    Votes: 0 0.0%

  • Total voters
    1
  • #1
1bobwhite
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I've read the Fomalont and Kopeikin's experiment, and though very interesting and supposedly proves the speed of gravity, I feel there may be a very "simple" experiment that will make a comparison of the speeds, with an event that occurs every day, and may be tried by many groups with the measurement capabilities that are currently available on the ground.

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.

We know the sun's actual position is eight minutes shifted from the observed position, but I have not seen any experiments that try to demonstrate this.
 

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  • #2
DrGreg
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What do you think is the reason we see the sun at its brightest at midday? Do you think the sun itself gets brighter at 1152 and then we see the increase at 1200? :smile:

Once you've answered that, you should see there's a flaw in your proposal.
 
  • #3
bcrowell
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FAQ: How fast do changes in the gravitational field propagate?

General relativity predicts that disturbances in the gravitational field propagate as gravitational waves, and that low-amplitude gravitational waves travel at the speed of light. Gravitational waves have never been detected directly, but the loss of energy from the Hulse-Taylor binary pulsar has been checked to high precision against GR's predictions of the power emitted in the form of gravitational waves. Therefore it is extremely unlikely that there is anything seriously wrong with general relativity's description of gravitational waves.

It is difficult to design empirical tests that specifically check propagation at c, independently of the other features of general relativity. The trouble is that although there are other theories of gravity (e.g., Brans-Dicke gravity) that are consistent with all the currently available experimental data, none of them predict that gravitational disturbances propagate at any other speed than c. Without a test theory that predicts a different speed, it becomes essentially impossible to interpret observations so as to extract the speed. In 2003, Fomalont published the results of an exquisitely sensitive test of general relativity using radar astronomy, and these results were consistent with general relativity. Fomalont's co-author, the theorist Kopeikin, interpreted the results as verifying general relativity's prediction of propagation of gravitational disturbances at c. Samuel and Will published refutations showing that Kopeikin's interpretation was mistaken, and that what the experiment really verified was the speed of light, not the speed of gravity.

A kook paper by Van Flandern claiming propagation of gravitational effects at >c has been debunked by Carlip. Van Flandern's analysis also applies to propagation of electromagnetic disturbances, leading to the result that light propagates at >c --- a conclusion that Van Flandern apparently sincerely believes.

Fomalont and Kopeikin - http://arxiv.org/abs/astro-ph/0302294

Samuel - http://arxiv.org/abs/astro-ph/0304006

Will - http://arxiv.org/abs/astro-ph/0301145

Van Flandern - http://www.metaresearch.org/cosmology/speed_of_gravity.asp [Broken]

Carlip - http://xxx.lanl.gov/abs/gr-qc/9909087v2
 
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  • #4
1bobwhite
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DrGreg, I'm not referring to how bright the sun is, but the exact time when it is directly overhead. If it is sensed with a slit that passes a line across a sensor, then the area at the sensor gets brighter and brighter until the suns direct rays strike the sensor. If it is a spot then the same thing will happen.
An single aperature would act as a lens, which is not what is best, but a series of aperatures with black side cavities would allow most of the light to be trapped except what is direct to the sensor.
And the sensor can be biased to ignore light levels below the threshold of trigger, so that only the direct solar rays would be sufficient to trigger the sensor.
Bob.
 
  • #5
1bobwhite
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Hi bcrowell,



I'm not interested in looking for any waves. That's a different game. But if you want to think of it this way, a big gravity wave goes overhead every day. It has a peak to peak period of 24 hours. Ocean tides are the evidence of this intense gravity wave.

What I'm trying to get is the steady state pull "peak" (time of solar gravity pull that is directly overhead) that can be compared time wise to the time when the observed sun is directly overhead. We know the suns actual position is eight minutes ahead of the suns observed position.

If this steady pull peak can be determined, then it can be compared to the exact time of the observable light peak. If these peaks are coincidental, then gravity is at light speed, but if the light peak lags, then the gravity effect is faster than light speed.

Let's get some observations going, and then when the results are in, the ones who like theories can make up whatever they like to explain the data. Just please don't massage (bias) the data to make it fit the pet theories.
Bob.
 
  • #6
Ich
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DrGreg, I'm not referring to how bright the sun is, but the exact time when it is directly overhead.
DrGred had something else in mind. Is there day and night because the sun is revolving around the earth, or is earth rotating? What does this mean for your experiment?

Further, it's a bit more difficult than you think.
For example, if the sun were electrically charged, and we could measure the field of this charge here on earth, we would measure its direction to be not where we see the sun, but (almost exactly) where it ought to be now. For gravity, this "coincidence" is even more exact.
It's hard to explain in a few words, but those "forces" point to the momentary position rather than the retarded position of the source. Has to do with the absence of the respective modes in the radiation (no monopole radiation in EM, no monopole or quadrupole radiation in Gravity).
Read http://arxiv.org/abs/gr-qc/9909087" [Broken].
 
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  • #7
1bobwhite
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bcrowell, and DrGreg,


Solar gravity is the most powerful and immediately available force that can be studied by anyone with reasonably sensitive instruments. Even amateur researchers like myself, can make experiments that may be repeated and verified by more advanced and learned researchers.
With a forum such as this one, the value of an experiment may be determined by brilliant minds from all over this planet, and with enough amateur and professional experimental input from all over the world, the results may be reinforced and verified by experts with the result that possibly new knowledge may be obtained on the physics of the world that surrounds us. New knowledge is what science is all about.
Bob.
 
  • #8
1bobwhite
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Hi Ich,

By this experiment, I'm not trying to show what gravity is or isn't, but just trying to record the solar gravity effect upon the earth in a time frame that can be compared to the light arriving from the sun.
 
  • #9
DrGreg
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The "speed of gravity" can only apply to changes in gravity. The Sun's gravity is pretty constant, on a day-to-day scale, and the only significant changes we detect on Earth are due to the rotation of the Earth, not due to changes propagating from the Sun. Similarly the apparent brightness of the Sun is due to the Earth's rotation, not due to some effect propagating from the Sun.

So the two variations you propose to measure are both originating locally on the Earth, not eight light-minutes away. To put in another way, if you were in a spaceship hovering above the Earth, the 24-hour variation you refer to wouldn't occur at all.

An analogy: Suppose you are outside, and it so happens that there is wind blowing towards you from the same direction that you see the Sun. You spin round on a vertical axis and notice that the amount of sunshine in your face reaches a peak at the same time that the wind blows strongest into your face. Does that mean the speed of the wind equals the speed of light?
 
  • #10
1bobwhite
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Hi DrGreg,
Yes it is true, the earth rotates instead of the sun going around the earth, but for experimental purposes the sun still goes to its zenith at a certain TIME of the day. Its brightness is of no concern other than to trigger the sensor at the precise TIME it is at its zenith.

The solar gravity pull also rotates around the earth, with the peak of the distortion always being on the sun side. The ocean tides are a visual of this pull.

And no your analogy doesn't hold. These effect are not local, they both are influences on the earth from the very distant sun, so that even a spacecraft in orbit will sense the distortion caused by the solar gravity pull when it is on the sun side. Close to the earth it is in milligravs, but it is still measurable.

Since gravity cannot be stopped, chopped, throttled, or in any way modulated by man to determine its speed of propagation, with the possible exception of some recent magnetic antigravity effects, we have no way that I know of to measure its effects other than by its steady pull in relation to its instantaneous position in space from a known point on the earth at a specific time.

The earths distance from the sun can be a useful dimension to determine the time frames of light speed, in order to make these comparisons.

Regards, Bob.
 
  • #11
atyy
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  • #12
Dale
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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.
First of all, even the most sensitive detectors are still well below the sensitivity required to detect gravity waves, due largely to ever-present mechanical vibrations.

Second, even if they were perfectly sensitive the experiment would not accomplish your goal. As atyy and Dr. Greg (and perhaps others) already mentioned the gravitational field of the sun is not changing. So your experiment would only measure our motion through a static gravitational field, not the propagation speed of gravity waves. It turns out that gravitational waves require a quadrupole source, so we need to look at least at binary pairs of very massive objects in very tight orbits.
 
  • #13
1bobwhite
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All,

Once again I am NOT trying to detect or explain gravity "WAVES". And yes, todays absolute gravimeters have the sensitivities necessary for this experiment to proceed.

By the way, these gravity waves are still only a theory, yet so many people have described their properties, how they behave, and arguing whether they're being monopolar or quadrupolar, and on and on.

Hey, how about lets discover their existence first and then carefully observe and document their characteristics.

The same thing for the BIG Bang theory.
Nothing to date has proved the theory is viable that hasn't been shown by other theories that have verifiable evidence based on positional observation data.

Imagine if you will, being on a merry-go-round, that is located on the periphery of a much larger merry-go-round, which is located on a still much larger merry-go-round. Now try from your point of observation, to determine the speeds of motion, direction, and positional relationships of an object that is very far removed from all of these merry-go-rounds.
It is possible, but the possibility of error from so many unknowns, prohibits a conclusive determination of characteristics of the observed element.

Has it been determined yet where the center of rotation of our solar system is, or if it is revolving around some other much larger system?

If the current gravity data is examined carefully it can readily be seen that there is not a steady gravitational field, but a continuous moment by moment changing field. These changes haven't been adequately explained yet, but they are there to be examined.

Some amateur researchers have proposed that this changing field is the instantaneous response of overhead gravity influences from distant celestial bodies and systems. Maybe, but nevertheless they are readable, and open for interpretation.
Thoughts?
Bob.
 
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  • #14
Dale
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Once again I am NOT trying to detect or explain gravity "WAVES".
Then the title of your thread and your entire OP make no sense whatsoever. It is only gavity "WAVES" that can be associated with a speed. When you are dealing with a static spacetime there is no sense in which gravity has a speed.

This is similar to EM. EM "WAVES" propagate at c, electrostatic fields do not have a speed.
 
  • #15
Buckleymanor
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The "speed of gravity" can only apply to changes in gravity. The Sun's gravity is pretty constant, on a day-to-day scale, and the only significant changes we detect on Earth are due to the rotation of the Earth, not due to changes propagating from the Sun. Similarly the apparent brightness of the Sun is due to the Earth's rotation, not due to some effect propagating from the Sun.

So the two variations you propose to measure are both originating locally on the Earth, not eight light-minutes away. To put in another way, if you were in a spaceship hovering above the Earth, the 24-hour variation you refer to wouldn't occur at all.

An analogy: Suppose you are outside, and it so happens that there is wind blowing towards you from the same direction that you see the Sun. You spin round on a vertical axis and notice that the amount of sunshine in your face reaches a peak at the same time that the wind blows strongest into your face. Does that mean the speed of the wind equals the speed of light?
On a day-to -day scale the sun's gravity is pretty constant.What about from year-to-year or rather six months-to-six months.
Eliptical orbit of Earth, closest to the sun in winter, furthest away in summer, gravity stronger in winter than summer, do experiment.
 
  • #16
cesiumfrog
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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.
I think you're misunderstanding their responses.

For simplicity, imagine if the earth were not orbiting the sun and rotating on its axis. Instead, let the earth be fixed and let the sun fly past the earth (just once, with constant velocity. Let's say the closest point of its trajectory is 8 light-minutes away, and it is at 0.5% of lightspeed so that at peak it still advances through our sky a quarter degree per minute).

They're saying, you will indeed measure the 8 minute lag! But it's even worse than you expected: say you also try to measure the slight electric field of the sun. Then you'll measure the same lag again: the direction of the mean electric field will be 2 arc-minutes of a degree ahead of the direction of mean solar EM wave irradiation. The mathematics that supports this is worth reading.

We know the sun's actual position is eight minutes shifted from the observed position

Do we know it? Can you cite some reference to show that fact isn't just false?

The above example needed 0.5% of light-speed to imitate (by linear motion) its apparent motion (as we pretty much "rotate on the spot") (!). Actually, the relative motion due to Earth's orbit is only 0.01% (of light-speed) plus 0.0001% for the surface's rotational speed. That should correspond to only a couple arc-seconds (at 8 light-minutes), a lag of a tenth of a second from the observed position..

But as before, it doesn't prove anything new, even if you can detect the visual position lagging the gravitational tidal force by a tenth of a second. You'd need to be able to detect whether or not gravitational fluctuations that are caused by non-terrestrial disturbances like solar flares arrive eight minutes early. To build such a sensitive detector is basically what the laser interferometer people are trying.
 
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  • #17
1bobwhite
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cesiumfrog,

For an answer to your question;
Originally Posted by 1bobwhite
"We know the sun's actual position is eight minutes shifted from the observed position"
"Do we know it? Can you cite some reference to show that fact isn't just false?"

I an using information from www.metaresearch.org[/URL] :


[How then does the direction of Earth’s acceleration compare with the direction of the visible Sun? By direct calculation from geometric ephemerides fitted to such observations, such as those published by the U.S. Naval Observatory or the Development Ephemerides of the Jet Propulsion Laboratory, the Earth accelerates toward a point 20 arc seconds in front of the visible Sun, where the Sun will appear to be in 8.3 minutes. In other words, the acceleration now is toward the true, instantaneous direction of the Sun now, and is not parallel to the direction of the arriving solar photons now. This is additional evidence that forces from electromagnetic radiation pressure and from gravity do not have the same propagation speed.]

This explanation also helps to stimulate the search for that gravity peak for the time check, to verify the propagation speeds experimentally.
 
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  • #18
cesiumfrog
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I an using information from www.metaresearch.org:[/URL]

[How then does the direction of Earth’s acceleration compare with the direction of the visible Sun? By direct calculation from geometric ephemerides fitted to such observations, such as those published by the U.S. Naval Observatory or the Development Ephemerides of the Jet Propulsion Laboratory, the Earth accelerates toward a point 20 arc seconds in front of the visible Sun, where the Sun will appear to be in 8.3 minutes. In other words, the acceleration now is toward the true, instantaneous direction of the Sun now, and is not parallel to the direction of the arriving solar photons now. [B]This is additional evidence that forces from electromagnetic radiation pressure and from gravity do not have the same propagation speed.[/B]][/QUOTE]

You've made two mistakes.

1. Rather than directing us to where we can read that quote in context, you've only linked to some broader site, expecting us to have time to guess and search out the precise paragraph you're referring to. Where is the direct calculation that your quote mentions?

2. Your source, metaresearch with motto "challenges to mainstream paradigms", is obviously a crackpot website (apparently the recently deceased Tom Van Flandern) rather than an independent reputable source for reliable information.

By the way (if it wasn't already obvious to you), "the direction of earth's acceleration" (in the context of your quote) [U]is[/U] the direction of the sun's gravitational force (in the context of your original question).
 
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  • #19
Dale
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This explanation also helps to stimulate the search for that gravity peak for the time check, to verify the propagation speeds experimentally.
You are very confused. First, you speak of the speed of gravity, then you say that you are not speaking of waves, now you say that you are interested in propagation speed. A static spacetime does not propagate, only waves propagate.
 
  • #20
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You are very confused. First, you speak of the speed of gravity, then you say that you are not speaking of waves, now you say that you are interested in propagation speed. A static spacetime does not propagate, only waves propagate.
Spacetimes in GR, including non-stationary spacetimes, which by definition include gravitational waves, never change as they include time.
 
  • #21
Dale
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I don't know your background, but a static spacetime is a special class of spacetimes where there are no gravitational waves. What the OP is describing would detect only that static spacetime curvature from the sun.

http://en.wikipedia.org/wiki/Static_spacetime
 
  • #22
Passionflower
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a static spacetime is a special class of spacetimes where there are no gravitational waves.
Correct by definition all stationary spacetimes, and static spacetimes are a subset of that, do not contain any gravitational waves. I suppose I was confused by your statement: "A static spacetime does not propagate, only waves propagate".
 
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  • #23
Dale
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Sorry if it was confusing, I was trying to keep it as simple as possible for 1bobwhite's understanding and may have gone overboard.
 
  • #24
1bobwhite
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All,

You may use whatever terminology you wish and apply whatever theories that are of interest to you, but what I am trying do is engineer and construct an apparatus for the purpose of detecting and earth time frame referencing the gravity pull of the sun.

You guys can help by making suggestions as to how to accomplish this. I really don't care what theories are out there, I'm trying to take the measurements.

After the data is in, then it can be applied as necessary to what the theorists desire.

And cesiumfrog, since you dont understand what a "crackpot" web site is saying then how about this one: http://iopscience.iop.org/0004-637X/590/2/683/fulltext

Be sure to read this one carefully as it has all the math you can stand and answers most of the questions that are being asked in this thread.

Before you make any more of your statements, consider what you have read as there may be a quiz afterward.

Regards, Bob.
 
  • #25
cesiumfrog
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[..]what I am trying do is engineer and construct an apparatus for the purpose of detecting and earth time frame referencing the gravity pull of the sun.
[..]
And cesiumfrog, since you dont understand what a "crackpot" web site is saying then how about this one: http://iopscience.iop.org/0004-637X/590/2/683/fulltext

Be sure to read this one carefully as it has all the math you can stand and answers most of the questions that are being asked in this thread.

Before you make any more of your statements, consider what you have read as there may be a quiz afterward.
ABSTRACT

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. Using the post-Newtonian approximation, we consider an expansion in powers of v/c beyond the leading "Shapiro" time-delay effect, while working to first order only in Gm/c2, and show that the altered propagation speed of the gravitational signal has no effect whatsoever on the time delay to first order in v/c beyond leading term, although it will have an effect to second and higher order. We show that the only other possible effects of an altered speed cg at this order arise from a modification of the parameterized post-Newtonian coefficient α1 of the metric from the value 0 predicted by general relativity. Current solar-system measurements already provide tight bounds on such a modification. We conclude that recent measurements of the propagation of radio signals past Jupiter are sensitive to α1 but are not directly sensitive to the speed of propagation of gravity.

I'm not exactly what part of the article you're saying is relevant? They assume, rather than find, a different speed. (In fact they seem to be saying evidence is already stacking against the speed actually being different.) It seems nowhere to describe the angle that you're directly interested in? And they're referring to the speed at which changes in the gravitational field radiate, whereas you are interested in a field that is static. (Nothing wrong with the idea of explicitly measuring the speed of gravitational radiation, but you shouldn't ignore what the experts have found about the ways of doing so.)
 
  • #26
Dale
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I really don't care what theories are out there, I'm trying to take the measurements.
Then why are you discussing it here, go make the measurements.
 
  • #27
1bobwhite
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cesiumfrog,

Maybe this article you'll find satisfactory for the explanation.

http://crib.corepower.com:8080/~relfaq/grav_speed.html [Broken]

Please read up on the function of the assumption and intuition in the process of theory evaluation. It is not what you may think. All accepted "facts" start with an assumption.

Regards,
Bob
 
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  • #28
Dale
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It is interesting that you post that particular link since it supports what everyone else has been saying.
 
  • #29
1bobwhite
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DaleSpam,

The synopsis of the article is that the experiment to prove that speed of gravity supposedly is the speed of light using Juptier and the distant celestial body signals, did not succeed to show the speed of gravity, but only reaffirms the GR speed of light, and that the speed of gravity propagation has yet to be determined by experimental means.

Regards,
Bob.
 
  • #30
Dale
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What it showed is that the effect of the finite speed of gravity is a second-order effect and cannot be determined by first-order experiments like the one in the article or the one you are proposing. As everyone has been telling you.
 
  • #31
1bobwhite
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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.
 
  • #32
Russell E
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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.
 
  • #33
1bobwhite
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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.
 
  • #34
ZikZak
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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.
 
  • #35
Dale
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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.
 

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