# light propagates at c + v?

Discussion in 'Alternative Theories' started by BdS, Nov 21, 2015.

1. ### BdSRegistered Senior Member

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455
Because its not instant in GR and you claim gravity doesnt travel at c + v, then logically you have to calculate the earths orbit from where the sun generated that curve segment where it was was 8 mins ago.

3. ### brucepValued Senior Member

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Like I said what you imagine it to be is bullshit. Why would that be true? Figure it out. Probably because you can't imagine a local theory of gravity where paths through the Galaxy have infinitesimal effects on the local spacetime curvature inside our gravitationally bound solar system. That's one reason why it's irrelevant. In science irrelevance is something that doesn't have any measurable effect on empirical results or to theoretical predictions.

5. ### FOLZONIRegistered Senior Member

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Only Einstein's GR claims that gravity is propagated at the speed of light.

In Newtonian gravity, Newton was forced to concede that gravity acts instantaneously at a distance - in order to get his equations to work.

Since however light takes nearly 8 minutes to reach us from the sun, if we could find detect the exact direction of gravitational pull, we could determine whether Newton or Big Al Einstein was right.

This is because the direction of the Newtonian gravitational pull would be about 2 degrees ahead of the sun's visible position in the sky. But can we measure that?

Surprisingly, there may be a way to do so. In New Scientist there was a recent article claiming that certain plants' leaves which droop at night seem to rise up to near-daytime levels when the moon is passing overhead. This was thought to be the effect of moonlight, but when experimenters covered the plants from any moonlight or other light sources the leaves of the plants still raised up. Hence the experimenters now think this is the gravitational effect of the moon itself - though if this were the case one would expect the centrifugal force on the opposite side of the earth to the moon would also raise up the leaves. If the latter is shown to be the case (by studying the leaf-raising effects at spring and neap tides) then we could test the timing of the leaf-rising when moon and sun are close by, ascertaining the time of the peak centrifugal effect on the leaves when sun and moon are acting on them together! At present however we still need to demonstrate a centrifugal effect in opposition to the direct gravitational effect of the moon (since daylight observations are excluded by the sun's direct effect on the leaves).

FOLZONI

7. ### rpennerFully WiredValued Senior Member

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Not "only" -- also in any massless quantum theory, including string theory.
Irrelevant since Einstein replaces Newton based on the evidence.

That does not make sense because in either theory the Earth is in free fall. You would have to determine the tidal force due to the Sun which is swamped by the tidal force of the closer moon which is not itself easily measurable.

It's on the order of 80 picometers per second squared per kilometer. Very small at the lab scale. Or the plant scale.

Your calculation here makes no sense; you appear to be calculating $\frac{8 \; \textrm{minutes}}{24 \; \textrm{hours}} \times \frac{1 \; \textrm{hour}}{60 \; \textrm{minutes}} \times 360^{\circ} = 2^{\circ}$ where you have confused the apparent motion of the Sun due to the rotation of the Earth with the Earth motion about the Sun.

The New Scientist article is a pretty wacky idea.
https://www.newscientist.com/articl...y-could-govern-plant-movement-like-the-tides/
http://aob.oxfordjournals.org/content/116/2/149.long

Correlation is not causation and this doesn't seem to support the extraordinary claims.

Last edited: Nov 30, 2015
8. ### FOLZONIRegistered Senior Member

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The earth's rotation and its revolution around the sun are irrelevant in being separated here since we are considering specifically the direction of gravitational force (which, like weight and centrifugal force, is a vector quantity).
Einstein does NOT replace Newton since there is no evidence whatsoever for the gravitational impulse being transmitted at speed c. Newton's equations were used to go the Moon; Einstein's are but theoretical mathematical schlock which lead to logical paradoxes.

Hence the fact that astonished scientists found the leaves to rise up when the moon passed overhead without the light of the moon touching them remains a phenomenon to be investigated.

FOLZONI

9. ### brucepValued Senior Member

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All you're making is a shitload of ignorant assertions. Put a cork in it.

Last edited: Nov 30, 2015

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Not that simple folzoni my friend.

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html

Does Gravity Travel at the Speed of Light?
To begin with, the speed of gravity has not been measured directly in the laboratory—the gravitational interaction is too weak, and such an experiment is beyond present technological capabilities. The "speed of gravity" must therefore be deduced from astronomical observations, and the answer depends on what model of gravity one uses to describe those observations.

In the simple newtonian model, gravity propagates instantaneously: the force exerted by a massive object points directly toward that object's present position. For example, even though the Sun is 500 light seconds from the Earth, newtonian gravity describes a force on Earth directed towards the Sun's position "now," not its position 500 seconds ago. Putting a "light travel delay" (technically called "retardation") into newtonian gravity would make orbits unstable, leading to predictions that clearly contradict Solar System observations.

In general relativity, on the other hand, gravity propagates at the speed of light; that is, the motion of a massive object creates a distortion in the curvature of spacetime that moves outward at light speed. This might seem to contradict the Solar System observations described above, but remember that general relativity is conceptually very different from newtonian gravity, so a direct comparison is not so simple. Strictly speaking, gravity is not a "force" in general relativity, and a description in terms of speed and direction can be tricky. For weak fields, though, one can describe the theory in a sort of newtonian language. In that case, one finds that the "force" in GR is not quite central—it does not point directly towards the source of the gravitational field—and that it depends on velocity as well as position. The net result is that the effect of propagation delay is almost exactly cancelled, and general relativity very nearly reproduces the newtonian result.

This cancellation may seem less strange if one notes that a similar effect occurs in electromagnetism. If a charged particle is moving at a constant velocity, it exerts a force that points toward its present position, not its retarded position, even though electromagnetic interactions certainly move at the speed of light. Here, as in general relativity, subtleties in the nature of the interaction "conspire" to disguise the effect of propagation delay. It should be emphasized that in both electromagnetism and general relativity, this effect is not put inad hoc but comes out of the equations. Also, the cancellation is nearly exact only for constant velocities. If a charged particle or a gravitating mass suddenly accelerates, the change in the electric or gravitational field propagates outward at the speed of light.

Since this point can be confusing, it's worth exploring a little further, in a slightly more technical manner. Consider two bodies—call them A and B—held in orbit by either electrical or gravitational attraction. As long as the force on A points directly towards B and vice versa, a stable orbit is possible. If the force on A points instead towards the retarded (propagation-time-delayed) position of B, on the other hand, the effect is to add a new component of force in the direction of A's motion, causing instability of the orbit. This instability, in turn, leads to a change in the mechanical angular momentum of the A-B system. But totalangular momentum is conserved, so this change can only occur if some of the angular momentum of the A-B system is carried away by electromagnetic or gravitational radiation.

Now, in electrodynamics, a charge moving at a constant velocity does not radiate. Technically, the lowest-order radiation is dipole radiation, and the radiated power depends on the second time derivative of the electric dipole moment; two time derivatives give acceleration. So, to the extent that A's motion can be approximated as motion at a constant velocity, A cannot lose angular momentum. For the theory to be consistent, there must therefore be compensating terms that partially cancel the instability of the orbit caused by retardation. This is exactly what happens; a calculation shows that the force on A points not towards B's retarded position, but towards B's "linearly extrapolated" retarded position.

In general relativity, roughly speaking, a mass moving at a constant acceleration does not radiate. Here, the lowest order radiation is quadrupole radiation, and the radiated power depends on the third time derivative of the mass quadrupole moment. (The full picture is slightly more complex, since one cannot have a single, isolated accelerating mass; whatever it is that causes the acceleration also has a gravitational field, and its field must be taken into account.) For consistency, just as in the case of electromagnetism, a cancellation of the effect of retardation must occur, but it must now be even more complete—that is, it must hold to a higher power of v/c. This is exactly what one finds when one solves the equations of motion in general relativity.

While current observations do not yet provide a direct model-independent measurement of the speed of gravity, a test within the framework of general relativity can be made by observing the binary pulsar PSR 1913+16. The orbit of this binary system is gradually decaying, and this behavior is attributed to the loss of energy due to escaping gravitational radiation. But in any field theory, radiation is intimately related to the finite velocity of field propagation, and the orbital changes due to gravitational radiation can equivalently be viewed as damping caused by the finite propagation speed. (In the discussion above, this damping represents a failure of the "retardation" and "noncentral, velocity-dependent" effects to completely cancel.)

The rate of this damping can be computed, and one finds that it depends sensitively on the speed of gravity. The fact that gravitational damping is measured at all is a strong indication that the propagation speed of gravity is not infinite. If the calculational framework of general relativity is accepted, the damping can be used to calculate the speed, and the actual measurement confirms that the speed of gravity is equal to the speed of light to within 1%. (Measurements of at least one other binary pulsar system, PSR B1534+12, confirm this result, although so far with less precision.)

Are there future prospects for a direct measurement of the speed of gravity? One possibility would involve detection of gravitational waves from a supernova. The detection of gravitational radiation in the same time frame as a neutrino burst, followed by a later visual identification of a supernova, would be considered strong experimental evidence for the speed of gravity being equal to the speed of light. However, unless a very nearby supernova occurs soon, it will be some time before gravitational wave detectors are expected to be sensitive enough to perform such a test.
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The scientific world accepts that cosmology and gravity are best described by GR.
The scientific world accepts that the BB was the evolution of space and time as we know it.
Nothing comes close to describing what we see any better, and how they neatly fit snugly into each other like pieces of a jigsaw puzzle reaffirms their near certainty even more.
That's nothing to get too upset about but folzy.....Remember, these are learned reputable knowledgable men, that have far more credibility than either you or I.
Once you can accept that, your problems are halfway solved.

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https://www.newscientist.com/article/dn3232-first-speed-of-gravity-measurement-revealed/

First speed of gravity measurement revealed

The speed of gravity has been measured for the first time. The landmark experiment shows that it travels at the speed of light, meaning that Einstein’s general theory of relativity has passed another test with flying colours.

Ed Fomalont of the National Radio Astronomy Observatory in Charlottesville, Virginia, and Sergei Kopeikin of the University of Missouri in Columbia made the measurement, with the help of the planet Jupiter.

“We became the first two people to know the speed of gravity, one of the fundamental constants of nature,” the scientists say, in an article in New Scientist print edition. One important consequence of the result is that it places constraints on theories of “brane worlds”, which suggest the Universe has more spatial dimensions than the familiar three.

John Baez, a physicist from the University of California at Riverside, comments: “Einstein wins yet again.” He adds that any other result would have come as a shock.

12. ### FOLZONIRegistered Senior Member

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Gravitational waves have NEVER been found. Nor will they be - they are an artificial creation of an artificial theory, GR, whose claims have very different explanations. There is LESS chance of gravitational waves being discovered than there is of Saddam Hussein rising from the dead and being elected the next pope!

I.e. your internet-copied el-cheapo rantings are 100% meaningless.

FOLZONI

PS: The second article you quote, from a decade ago, is misleading. What is being measured is merely gravitational lensing by quasars - such lensing predicated by Soldner from Newtonian principles in 1803. I.e. the effect of gravity, not the speed of its effects which Newton had to admit were instantaneous in order to make his equations work.

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And BH's have never been seen, still we have overwhelming evidence supporting both. Fact: GR is overwhelmingly supported by science in general.
I would really honestly and logically say that most here see your unsupported nonsense as el cheapo rantings and even worse than meaningless for obvious reasons.
Fact: GR is overwhelmingly supported by science in general, because it is overwhelmingly evidenced by observations and experiments.
And, yes good evidence for Gravitational radiation does exist.
And of course GP-B has totally confirmed spacetime curvature and also the Lense Thirring effect.

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

In September 2002, Sergei Kopeikin and Edward Fomalont announced that they had made an indirect measurement of the speed of gravity, using their data from VLBImeasurement of the retarded position of Jupiter on its orbit during Jupiter's transitacross the line-of-sight of the bright radio source quasar QSO J0842+1835. Kopeikin and Fomalont concluded that the speed of gravity is between 0.8 and 1.2 times the speed of light, which would be fully consistent with the theoretical prediction of general relativity that the speed of gravity is exactly the same as the speed of light.[19]

Several physicists, including Clifford M. Will and Steve Carlip, have criticized these claims on the grounds that they have allegedly misinterpreted the results of their measurements. Notably, prior to the actual transit, Hideki Asada in a paper to the Astrophysical Journal Letters theorized that the proposed experiment was essentially a roundabout confirmation of the speed of light instead of the speed of gravity.[20]However, Kopeikin and Fomalont continue to vigorously argue their case and the means of presenting their result at the press-conference of AAS that was offered after the peer review of the results of the Jovian experiment had been done by the experts of the AAS scientific organizing committee. In later publication by Kopeikin and Fomalont, which uses a bi-metric formalism that splits the space-time null conein two – one for gravity and another one for light, the authors claimed that Asada's claim was theoretically unsound.[21] The two null cones overlap in general relativity, which makes tracking the speed-of-gravity effects difficult and requires a special mathematical technique of gravitational retarded potentials, which was worked out by Kopeikin and co-authors[22][23] but was never properly employed by Asada and/or the other critics.

Stuart Samuel also suggested that the experiment did not actually measure the speed of gravity because the effects were too small to have been measured.[24] A response by Kopeikin and Fomalont challenges this opinion.[25]

It is important to understand that none of the participants in this controversy are claiming that general relativity is "wrong". Rather, the debate concerns whether or not Kopeikin and Fomalont have really provided yet another verification of one of its fundamental predictions. A comprehensive review of the definition of the speed of gravity and its measurement with high-precision astrometric and other techniques appears in the textbook Relativistic Celestial Mechanics in the Solar System.

14. ### FOLZONIRegistered Senior Member

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Yes, p'boy, you highlight the important point.
They fall for GR - or loved the BS since they first heard of it - hence they contrive answers to fit with it and built upon the BS creating ever stupider theories e.g. Brans-Dicke Theory i.e. the material is interpreted in a tendentious way to make it appear to support GR, just as Einstein claimed that E=mcc supposedly proved SR!

FOLZONI

PS: I don't claim that the raising of the leaves during the moon's transit overhead is proof of the phenomena but it is merely one needing further investigation - and may yet provide an astounding proof! As opposed to the BS theorizing which is an integral part of developing a false theory, GR!

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SR/GR are totally overwhelmingly supported models of cosmology and reality, that at this time have no peer. Both have adhered to, and passed the scientific methodology and proper peer review.

One can only logically deduce two alternatives with regards to such overwhelming nonsense.
[1] You are suffering from delusions of grandeur as per my previous links.
[2] This is fun and games to you, to get a raise out of people through a methodology of supposed "shock and awe" tactics, which makes you are troll.

The first is probably the more serious malady of the two, and really should be treated.
The second shows a total amount of immaturity and stupidity.

False claims, false accusations, and actually reflects on a problem regarding anyone believing such fairy tales.

16. ### BdSRegistered Senior Member

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455
I look at it as how can it not be true and you've said nothing thats showing it not to be true. Unless we detect the drift in the OP.

Im trying to, but you're getting all defensive about it.

I can imagine it just fine from both views, its you that cant. You saying its not true because in GR your local frame is moving at v and then ignoring the v from there and saying it only travels at c to your local frame. From an external observers frame he sees it as c+v (the v of our local frame) or else you would need to calculate the orbit to the delayed c origin, to your local frame you seeing it as c and ignoring that your frame is moving at v. I dont consider it irrelevant just cause GR treats it in a different way, im looking at it from a different perspective.

Is the proof not already there by the manner in which you calculating the orbit? If you not calculating the orbit to where object was in the c delay time then it already proves gravity is moving at c + v or its instantaneously reconfiguring at v. Unless the object is leaving pings behind in space along its trajectory propagating at only c to the location it was emitted/created from, then we would detect a drift in the OP experiment, which I cant imagine to be correct, because then light would then not travel in straight lines in our local frame. If its propagating in straight lines to our local v moving frame then its not traveling in a straight line to the external observers frame, its traveling at c + v. Since the earth is orbiting the sun + rotating + orbiting the galaxy then it is actually c + v + v +v and becomes very complex. Which is why we just say c and ignore all the v's because we know its traveling at all those v's and we can ignore them all. Im here on earth and i shine a laser light straight up into space, i see it going in a straight line, but to a stationary space coordinate system the path was not straight, its a curved path at c + v + v + v.
Thats my opinion...

"In science irrelevance is something that doesn't have any measurable effect on empirical results or to theoretical predictions."
Treating the v as irrelevant because the maths is working without it, because of the way our theories are structured?

he didnt consider the gravity was moving at v, I would imagine thats why? or maybe it is instant? got to come up with an experiment to prove it...

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I accept that this is your opinion.
I also accept that you are entirely wrong.
I also accept that if you had any concrete substance in anything you say, you would not be here.
And finally I accept, that you have an agenda...a religious one, despite trying to keep it closeted.
Light travels at "c": ...Gravity is propagated at "c": Spacetime curves in the presence of mass: Space and time are non absolute entities that are entirely relevant and evidenced, which explains why c+v is just your own opinion, as you have admitted to.

18. ### KristofferGiant HyraxValued Senior Member

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Maybe the thread should be shifted to Alternative Theories or Pseudoscience?

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One can only surmise a sort of trolling "shock and awe" tactic for obvious purposes.
Or as shown previously, a religiously driven anti Einstein rant, that religious nuts are at times inclined to do.

20. ### brucepValued Senior Member

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That is one of my favorite experiments. There's still much controversy as to whether it was actually the speed of gravity or the speed of light which was measured. There isn't any disagreement with the measurement but a disagreement with how the measurement is modeled using this mathematical physics model.
https://en.m.wikipedia.org/wiki/Parameterized_post-Newtonian_formalism
The two main desenters are Professors Steven Carlip and Clifford Will. With Professor Will being the author of the .... Post-Newtonian_formalism. You can find Professor Kopeikin's papers on the Jovian Speed of Gravity experiment [arxiv] and the disagreement follows through citations. It's the method at work. Great reading. I wonder if rpenner is familiar with this? He could possibly give an opinion on whether he feels the formalism was used correctly. It's a far out experiment and I would like to believe the speed of gravity was measured. But .........

21. ### DaveC426913Valued Senior Member

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Einsteinian gravity does not travel. It is an existing curvature in existing spacetime. The part of the curvature that we are on is already here; it doesn't take 8 minutes to arrive.

(< digression > This incidentally also explains how gravity from a black hole can affect nearby bodies. Newtonian gravity would not be able to escape a black hole< /digression >)

What takes time to arrive is gravitational waves, or changes in gravity.

Your next question is going to be 'so what if the sun suddenly disappeared'. The short answer is: it can't.

Last edited: Dec 1, 2015
22. ### brucepValued Senior Member

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Think you're pretty funny? You're an illiterate fool. LOL. All the knowledge in the world is off no use to fools. The Eagles.