We are, ultimately, preparing the field to discuss the possibility of QM effects, or others, on the formulation of gravity, and how they would not be forbidden by SR or GR. This is, essentially, a logical dicussion open to anyone, that can also free the logical mind.
This goal is forbidden by current general relativity theory, that defined the speed of gravitational waves to be c=1, the speed of light in vacuum [1]. However, we conjecture that gravity waves, using a different formulation of gravity, such as quantum mechanics, not using the curvature of spacetime to represent gravity, could allow such results to be calculated.
The reasoning is explained as follows. First, we prove that current general relativity may include a basic circular argument. Second, this may hide or mask other formulations. Third, this enables the conjecture of this question, including any value for wave speed.
1. Circular definitions are self-referential, a tautology, trivially right. For example, "a circle is a circle". Or, they can involve more complex patterns, where the repetition is hidden in multiple cycles, hard to see, with components that are defined by components. But, such definitions carry no information, in Shannon terms. They are useless to define the problem. Considering the subject of Physics, a specific number of definitions seem circular. For example, the definition of a travelling wave, as a "wave pattern that is seen travelling through a medium", as often stated, even in current textbooks used in the US Ivy League universities.
Current general relativity may include a basic circular argument, in that the Minkowsky metric uses c=1 for an electromagnetic wave in flat spacetime, and then measures the deformations of a curved spacetime (now, gravitational waves) by using the same value of c=1. Here, one has to suppose X, and using X “justifies” one to use it. Another argument, with a similar circular falllacy, is that since gravitational waves are massless yet have a finite energy, they must move at the speed of light
2. This fallacy, which seems to have not been observed before in general relativity, is similar to other “definitions” yet accepted in physics. This could be, as in a "mandatory" but questioned vector potential in electromagnetism [2], "a sleight of hand that is just, perhaps, hiding a circular argument, ending in a self-reference that is correct by that same definition". Thus, this is is not false necessarily, but may be incomplete -- it may hide a formulation where gravity waves are superluminal, c > 1, or have any speed value.
3. Thus, by not accounting for solutions that may be superluminal, or at any speed, current general relativity is blind to them. Even c=1 solutions may be missed by general relativity.
This may be important for currently missing solutions, such as in Dark Matter.
NOTES:
a. This discussion is about a logical fallacy in GR. It is NOT about any experiment, but the theory that represents nature. SR is powerless to define it, or any experiment.
b. This has an inverse relation to what is seen experimentally today, that what we do not measure is, maybe, possible. We don no have to recall the many cases where this happened before in science, and there are many examples in QM, today's perceived "bane" of SR and GR. We are discussing the possibility of QM effects on our formulation of gravity, and how they would not be forbidden by SR or GR.
c. To consider superluminal effects in gravity can be seen as a bet that gravity as that (v > c) wave can escape from colliding black holes, and reach distant Earth, an experimental fact maybe measured by LIGO, ahead of the detection time considered by LIGO themselves, of conventional gravity waves modeled by a spacetime curvature (that must, by construction, travel at c).
d. We are NOT talking about conventional gravity waves, a curvature in spacetime (see discussion theme, above), where gravity waves must follow the speed of light in vacuum, by construction.
e. Superluminal effects are also a verifiable solution of Mexwell's equations, as the late Waldyr Rodrigues considered. These are not so-called "academic" pursuits, decried by Murray Gell-Mann, but real contributions to understand both nature and the equations that describe it. Do they match? Is something over-promised in the equations, or falsely denied?
f. We point out here that current gravitational theory as indicated by general relativity has a basic fallacy. The argument is still in development, but it indicates a logical conjecture, that superluminal solutions may exist for gravity waves, they are not prohibited by general relativity.
g. And, we may also need to begin earlier, by denying Newtonian conventionalisms that still beset modern physics! A version of that is available for comments at the last update, here:
https://www.researchgate.net/project/Research-May-we-need-to-abandon-the-Standard-Model-in-Physics-What-could-be-next?_sg=ZSSDBmxd_Ik2JWs4ZX1an6RGQxpW28jehnp9mZonSCV1pd4bbOmYBOndmyVw7H70ESOtQZNIFica3oCfkOUR5tcr9r0ENuOvkmjX
h. Off this discussion topic. but may be worth mentioning here. This is not a conceptual choice only, but must be also experimental, which one could then call natural, it is in nature. Reality, experimentally, must be at least 4D as in spacetime, it “does not fit” inside 3D in all cases. This is not 3+1, it is 4, integrated, you cannot separate. Now, this does not mean that reality cannot be >4 in dimensions, and exceed c in that context, of 8D or more... Gravity may be modeled in higher dimension than four, then. This is, today, speculative, but it is useful to know that v > c is not forbidden for gravity by SR, considering this discussion.
9. This thread arrived, in the past, at a conclusion, which is stated in the body of the initial text. There is no room to refuse to notice an obvious thing, or to re-explain here, the reasoning and references are available here, to anyone.
10. We are now ready to move to non-mathematical and non-physical aspects. We are talking about the historical and intersubjective aspects, which are important to us qua humans. Finding a humanly acceptable answer is difficult in physics or maths today, and, pretty soon, in all natural sciences. Therefore, this very thread is important.
11. We suggest, as in physics, that facts are what you were willing to bbelieve. A bias, preventing a more complete vision. That is another motivation here, to abandon bias. It has no place going forward, and may prevent us from seeing what is plain to see.
[1] LIGO CALTECH, https://www.ligo.caltech.edu/page/what-are-gw
[2] E. V. Gerck, Available from: https://www.researchgate.net/publication/325934158_There_Must_Be_Light
Ian Proffitt: " If Space is expanding then I assume it does so uniformly. "
Hi Ian! I doesn't seem to be. If expansion can be taken as a measure of timeflow, and time runs fractionally faster in intergalactic voids than in galaxy-rich regions (converse of gravitational time dilation), then those voids will tend to expand slightly faster, giving us a positive feedback effect (a bit like when you over-inflate a bicycle inner tube, and the thinner regions "balloon" out). If the universe starts out with its massenergy fairly evenly distributed, the slightest variation in density causes the less-dense regions to expand faster, becoming even less dense, causing a lobed structure.
The surface of the resulting universe isn't so much like the pitted skin of an orange (dotted with little gravity-wells, regions where the surface has a slightly smaller distance from the centre due to gravitational time-dilation), it's more like the surface of a raspberry, a series of faster-expanding lobes or voids that tend to expel matter, with most matter pushed together into the "cracks" between the lobes by the uneven expansion.
Large-scale surveys of galaxy distributions do seem to show this sort of distribution, a series of interlinked voids, with galaxies concentrated in the walls between adjacent voids, or in filaments where typically three or more voids (or three or more intervoid walls) meet.
http://www.2dfgrs.net/
It seems to be essentially an irregular foam-like structure.
While the "foamy" structure can be explained by differential positive-feedback expansion, other attempts to explain it have run into trouble. One of the big problems is that it takes so long for light to cross a void, that nobody seems to understand how a void can self-regulate to have such uniformity across its walls. If you think of the walls as being the primary structures, it doesn't seem to work. How does a wall communicate with its opposing wall? However, if the voids are the primary structures, and are expanding, things seem to be easier to explain.
Other than the void structure, the second prediction associated with differential expansion would be that we would be allowed to see isolated stars in the middle of deep voids whose age appears to be greater than the assumed age of the universe. This would be because more cosmological time has elapsed for matter in a deep void than it has for most of the universe's inhabitants, who wil ltend to be living in "galaxy wall" regions.
https://www.researchgate.net/post/The_below_link_clearly_proves_particles_can_exceed_the_speed_of_light_but_less_than_500000km_s_Maybe_they_are_ghost_particles_Are_they?_ec=topicPostOverviewAuthoredQuestions&_sg=bo9fi57qs2O1UrnEQmnyulXsu9boeohkXssV69SRZQSTOlSy4d26pHNwxEeShdsm18FOf-W9tbrNNdq7.sxK3PjqczTdPZGNxB1j8_meY9rM7Xc55Hc7tnc0zfy-P1Tyh4uwPvuFu_zkniPm82Nky_ydzFtWdEjp0daFK5tg
Quite right Ed
The speed of the graviton may be greater than c - hence it can escape a black hole.
Gravity as an emergent property is nonsensical given we have detected gravitational waves
The speed of gravitational waves matches that of light to a few parts in 10-15 or better:
http://iopscience.iop.org/article/10.3847/2041-8213/aa920c/pdf
Hello all: Thank you.
To consider superluminal effects in gravity is a bet that gravity as that wave can escape from colliding black holes, and reach distant Earth, an experimental fact maybe measured by LIGO, ahead of the detection time considered by LIGO themselves, of conventional gravity waves modeled by a spacetime curvature.
This fits with Andrew Worsley comments. On George Dishman comments, we are NOT talking about conventional gravity waves, a curvature in spacetime (see discussion theme, above), where gravity waves must follow the speed of light in vacuum, by construction.
I note that superluminal effects are also a verifiable solution of Mexwell's equations, as the late Waldyr Rodrigues considered. These are not so-called "academic" pursuits, decried by Murray Gell-Mann, but real contributions to understand both nature and the equations that describe it. Do they match? Is something over-promised in the equations, or falsely denied?
In that sense, we point out here that current gravitational theory as indicated by general relativity has a basic fallacy. The argument is still in development, but it indicates a logical conjecture, that superluminal solutions may exist for gravity waves, they are not prohibited by general relativity.
But we also need to begin earlier, by denying Newtonian conventioalims that still beset modern physics!
A version of that is available for comments at he last update, here:
https://www.researchgate.net/project/Research-May-we-need-to-abandon-the-Standard-Model-in-Physics-What-could-be-next?_sg=ZSSDBmxd_Ik2JWs4ZX1an6RGQxpW28jehnp9mZonSCV1pd4bbOmYBOndmyVw7H70ESOtQZNIFica3oCfkOUR5tcr9r0ENuOvkmjX
Hello Ed,
EG: On George Dishman comments, we are NOT talking about conventional gravity waves, a curvature in spacetime (see discussion theme, above), where gravity waves must follow the speed of light in vacuum, by construction.
What I have pointed out is that we now know they travel at speed c by observation, hence any theory that predicted that they would travel faster than c (or slower) has now been falsified by that observation.
Hello George: That's not how we do it in physics -- whether the theory does or does not prohibit, and it has in our view a circular argument flaw that is clearly explained above, the data may have not been measured it, or it may have a precursor that the algorithm does not forecast, and so it was not detected, or (whatever).
For example, it is a common mistake to think of a hypothesis as a guess or a prediction, or to assume that a hypothesis must include cause and effect. Another common error is to think that in science a YES means “true” and a NO means “false.” With the growing importance of science and scientific arguments in today’s society, it is critical to avoid these and other pitfalls, in order to more effectively apply and contrast scientific principles in career and life.
In physics a YES means NOT YET FALSE, NO means MAYBE TRUE. The FALSE predominates, see https://www.researchgate.net/publication/313823676_The_Big_Idea_in_Physics_and_Science_The_Absolute
Hi Ed,
EG: That's not how we do it in physics
It is how it should be done, the scientific method says we develop theories based on observation.
EG: Another common error is to think that in science a YES means “true” and a NO means “false.”
I agree, a match to observation means "lives to fight another day" while a failure to match means "needs to be revised".
In this case the observation is that the speed is c with a low uncertainty.
Expansion of the universe will influence the speed of waves and shock fronts when they travel over long ranges. The same mechanism that deforms the field will also expand that field. It injects volume into the field and that volume will spread over the field. Without this mechanism there would be no volume in the universe.
Mass: http://dx.doi.org/10.13140/RG.2.2.10268.59528
Do 'waves' (and 'shock fronts') have a speed? Or are they simply markers of the passage of collective phenomena?
Ian,
The phase of the wave travels with defined speed. The front of a shock front travels with defined speed. The wave equation describes both phenomena. Shock fronts are not waves and cannot be represented by wave packages. Moving wave packages disperse and moving shock fronts do not disperse. The shape of the front is fixed. For one-dimensional shock fronts also the amplitude is fixed.
http://www.mathtube.org/sites/default/files/lecture-notes/Lamoureux_Michael.pdf, section 2.7
The only experimental evidence I know of super luminal information transfer is from the University of Geneva fiber optics tests on pairs of entangled photons from down divider crystals, and similar tests elsewhere. It has limited range after which decoherence occurs and the entanglement is lost. It is only demonstrated for quanta which can be described in Feynman sum over paths method, where superposition of states occur.
In physical objects made of more than about 30 fundamental particles, the classical laws apply where faster than light concept always results in complex energy, momentum, and mass. Imaginary part of complex quantities can be interpreted to mean the physical system cannot be physically described in 4D reference frames. That is to say faster than light is imaginary in 4D but might or might not occur as real in some higher dimensionality.
I don't support faster than light claims because the theories of Albert Einstein and Max Born allow light speed to increase locally in a stress energy field produced from kinetic energy. It dates from 1922 and is well documented, but not well understood or taught in the larger community.
Any macro energy device powerful enough to approach the regional speed of light is also powerful enough to increase the local speed of light as quickly as the device speed increases.
Special relativity allows a traveler to measure any speed of travel because of dilation, but never more than locally measured light speed. The observer who did not undergo the acceleration can only measure the regional speed of light. In some cases the differences in time and distance have been found to be real. In other cases maybe not.
For the question an observation of colliding neutron stars last year confirmed that gravity waves move at the same speed as gamma rays. Both were detected at the same time.
A chance for faster than light travel is found in the popular concepts of worm holes. This does not occur in 4D space time. It requires at least 6D and might be expressed in 12D or higher systems. In other threads I have shown how such higher dimensional systems can be constructed and measured.
My RG project from 2017 developed a concept based on scale relativity in which the scale of 4, at high energy represented flat 4D space inside a 6D warped field of kinetic energy stress curvature. It relates to squeezed quantum states, the TGD variation on GR, and hierarchy of Plancks.
In answer to the question, there are various theories and claims, but the observational evidence says gravity waves move at light speed the same as gamma rays when observed from Earth. Travelers moving with the waves could measure higher speeds. Please notice that Travelers have many possibilities that can not be observed by others who don't travel. Also the quantum scale allows FTL of entanglement through superposition of states that are averaged out on larger scales.
Reply to Ed Gerck.
First I should agree with you that popular metrics of GR are in error by assuming constant light speed in solving field equations, then using the same metrics to argue for constant light speed. Einstein did not do this as I pointed out in the previous comment. Also Max Born did not make the mistake in his book of 1924. Einstein allowed local light speed to change in curved space time. In other threads I pointed to his equation 107 and nearby paragraphs in Einstein's technical book of 1922.
Contrary to arguments some of the metrics can be used to predict that light speed changes with stress energy curvature, proving that the assumption of constant light speed was not correct in developing the metric. There is an old exercise in which the predicted light speed function is put back into the development of an improved metric several times until the predicted light speed is the same as the assumption. In fact Einstein did this by setting (ds)2 equal to zero, causing the metric to describe the propagation of light. Then (dr/dt) becomes the local light speed and c of the metric becomes the regional light speed.
The Einstein method gives a conclusion for non rotating central mass in GR.
L = (dr/dt)/c = ( 1 - 2MG/r/c2 )
It means that gravity decreases local light speed, and that referring to LaGrange Method kinetic energy increases local light speed. This is how my previous comment relates to the question.
Einstein field equations have an approximation of truncating higher order terms that would lead to 6D or 12D concepts at high energy, supporting FTL through worm holes some of which may be spontaneous, but the mistake you are asking about occurs in solutions of field equations, not in the field equations.
Result is that popular metrics are accurate in the low energy cases, but not adequate when the energy density becomes very large. Also the light speed is taught incorrectly almost everywhere, and written into law.
My point is that more than one mistake is found in popular thought of GR. If you fix one of them you should fix the others also.
At the risk of garnering more hidden down votes, from our less overt colleagues who are died in the wool relativists. I have to agree with Ed Gerck.
In answer to George Dishman's comment the speed of gravitation may well be the speed of light in ordinary space time, but can be greater inside a black hole. The average remains the speed of light in the black hole. But one set diverges to go faster than the speed of light to form a bifurcation we see in black hole mergers but not seen in neutron star mergers.
Meaning that inside a black hole gravitational waves do go faster than the speed of light. Otherwise how would they escape the black hole.
Hello Ed,
To answer what is superluminal speed we have to understand what that means. In SRT we describe how objects move with the help of a Minkowski diagram. In that diagram we draw the speed of light movement as a 45° angle line. From there to horizontal the lines are levels of simultaneity where the lines from 45° to vertical are possible worldlines of objects moving with a velocity less than the speed of light. The first sector describes events that are spacelike separated. The second sector are events that are time like separated.
A gravity wave that passes one observer at one moment in time and place, event 1, and continues to go to another observer at a different moment in time and place, event 2, can have a velocity larger than c if these events are spacelike separated. Depending on the velocity of the frame where these two observers are at rest the two events could be simultaneous, they could be sequential, first event 1 and then event 2, or they could be anti-sequential, first event 2 and then event 1.
So, as long as SRT is used we have to conclude that any speed faster than the speed of light will result in a situation where for some IRF this speed is seen as moving backward in time. That makes a gravity wave moving with superluminal speed a problem.
Of cause I am talking about a speed of the wave perpendicular to the wavefront.
Regards,
Paul Gradenwitz
Hello Paul Gradenwitz, Andrew Worsley, Jerry Decker, and all: Thank you. We conjecture that gravity waves, using a different formulation of gravity, not using the curvature of spacetime to represent gravity, could allow such results to be calculated. This has nothing to do with spacetime properties, or Lorentz transformations. They do NOT impose limits to what is outside of their formulation.
In this specific purpose, the discussion here is about a fallacy that we found in the formulation GR, which uses spacetime to limit spacetime. It has no exterior principle that must limit the propagation of gravitational waves, gravity is SUPPOSED to be a form of electromagnetism? Only then, it would work as a restriction, we suggest.
Thus, if gravity is not a form of electromagnetism, we are using the wrong limit to describe gravity waves. Maybe some of those waves conform to v = c, others do not. There would be no prohibition from special relativity. Can we find a new formulation to explain gravity? Spacetime remains, it is a law in the universe. Just not setting the highest limit of information transfer, which would then be explained by gravity's alternative formulation.
Cheers, Ed Gerck
Don't forget that reality presents events in Euclidean coordinates and that observers perceive in spacetime coordinates,
Hi Andrew,
AW: At the risk of garnering more hidden down votes ...
RG removed the down-vote facility some time ago.
AW: In answer to George Dishman's comment the speed of gravitation may well be the speed of light in ordinary space time, but can be greater inside a black hole.
A GW passing close to a BH (or any other mass) must be bent by exactly the same amount as light for the GW and the gamma burst from GW170817 to have arrived at the same time. Both were delayed by around 400 days due to the Shapiro delay but the delays matched to within a fraction of a second.
A GW entering a BH horizon like everything else could not come back out. AW: Meaning that inside a black hole gravitational waves do go faster than the speed of light.
Inside the horizon, they would move at c relative to local matter also inside.
AW: Otherwise how would they escape the black hole.
They don't. GW from a pair of merging BH are generated about ten times farther away from the centre of the binary system than the separation between the bodies.
Hello Ed Gerck ,
I didn't specify what a gravity wave is made of. Yes in GRT the wave is a wrinkle in spacetime. It can be something else in another theory. Yet there is a problem with what you call faster than light speed. To measure a speed you have to define time at two locations that are separated. So I don't pose a limit with any Lorentz Transformation. I only point out that understanding what is a faster than light travel time could have some problems.
Also the observations, where both a GW and a light event reached us with a fraction of a second difference are an indication that gravity waves seem to move with the same speed as light. The information that these two events came at about the same time at earth is based on light speed dependent clock synchronisation. Whatever synchronisation used the deviation of clocks is such that light would pass earth in less then one second. So for me this result reads as that both arrived at more or less the same time under the condition that the light signal and the GW are indeed from the same source.
Regards,
Paul Gradenwitz
IMO There's an inherent definitional nastiness with the idea of asking the speed at which gravitational waves propagate, as they're meant to propagate at c (and IMO doubtless do), but the presence of the wavefront can represent a change in background c.
So suppose that we have an oscillating piston, whose velocities and accelerations create lightspeed anisotropies, first in one direction and then in the other, and these changes propagate away from the end of the piston as gravitational waves, alternately increasing and decreasing the velocity of light as defined along the piston axis w.r.t. background.
If we take the part of the wavecycle that represent a progressive increase in the speed of light (perhaps from a lowered starting value), then the front of the wave represents a lower speed of light than the back of the wave. Which means that if both parts propagate at their nominal local light velocity-values for that direction, the back of the wave should be trying to catch up with and eventually overtake the front.
This is obviously not allowable. Apart from anything else, a compacting gravitational wavefront might be expected to increase energy as it decreases wavelength, which would be Very Bad. So we're dealing with the confusing nonlinear behaviour characteristic of an acoustic metric, where the nominal signal propagation velocity is altered by the presence of the signal itself.
In the classical description, the velocities are "smeared", and the front of the wavesection advances into the region ahead a little faster than otherwise expected. In the quantum description, the region directly ahead of the wave is preconditioned with information about the impending velocity-increase, and receives the signal faster than strictly "official" local c, via the information quantum-tunnelling forwards through what would otherwise be an absolutely unbreachable signal barrier. This means that the ability of the gravity-wave to propagate without causing paradoxes can be described in terms of Hawking radiation effects.
The problem with an "acoustic" gravitational wave is that as the wave "smears", the different parts of the wave may tend to cross-contaminate leading to the wave progressively self-extinguishing. It's be useful to know how strong this expected energy-loss might be as a function of distance travelled.
The energy-loss doesn't necessarily violate conservation laws: if the progressive straightening out of the wave as it travels can be visualised as the straightening-out of a propagating kink in spacetime (which not everyone will agree with), then this might be associated with an increase in length or spatial distance along the path.
In this scenario, if we have a double-star throwing gravity-waves out into its environment from its equator, and those waves are converting some of their curvature into additional spacetime, then if we look at the double-star from the equatorial plane, it'll seem further away. If it seems further away for all equatorial observers, then the distortion appears as an apparent deepening of the star's gravity-well: at least some of the energy apparently lost by the radiated wave will appears to have been left behind in the region around the gravity-source, and still present as gravitational curvature.
Does anyone know if this energy-loss has been calculated?
The universe is a field. Without further knowledge it is irresponsible to state things about this subject. It is better to start from a platform in which this field exist and let that platform determine its properties and behavior.
A suitable platform that is familiar for many physicists is a Hilbert space. Hilbert spaces exist as separable Hilbert space and as non-separable Hilbert space. Hilbert spaces can only cope with number systems that are division rings. Only three suitable number system exist. The real numbers, the complex numbers and the quaternions. The quaternions are ideally suited for the storage of dynamic geometric data in the form of a scalar time-stamp and a three-dimensional spatial location vector. As eigenvalues of operators they can store discrete sets of such values in the eigenspace of operators that reside in separable Hilbert space. For example all rational values of a quaternionic number system can together form an eigenspace of a special reference operator. When equipped with Cartesian and polar coordinate systems this reference operator can manage the private parameter space of the separable Hilbert space. This fact can be exploited for defining a category of defined operators that use the eigenvectors of the reference operator and that specify the eigenvalue for an eigenvector as the target value of a selected quaternionic function that corresponds with the eigenvalue of the reference operator as parameter value for that function. This defines the eigenspace of such defined operator as a sampled continuum or with other words, as a sampled field.
If this separable Hilbert space has infinite many dimensions, then it owns a unique non-separable companion Hilbert space that embeds its separable partner. In this non-separable Hilbert space a similar reference operator exists that manages a continuum private parameter space. A category of defined operators exist that manage continuum eigenspaces that are defined by corresponding quaternionic functions. These continuums represent properly defined fields whose properties and behavior is completely defined by quaternionic function theory. This approach merges Hilbert space operator technology with quaternionic differential and integral calculus.
Two quaternionic homogeneous second order partial differential equations exist of which one corresponds to the well known wave equation. That equation describes the behavior and properties of quaternionic waves. Within the set of solutions of these equations exist pulse responses that act as shock fronts. The spherical pulse response temporarily deforms and persistently expands the quaternionic field.
See: BehaviorOfBasicFields; http://dx.doi.org/10.13140/RG.2.2.15517.20960
and Mass: http://dx.doi.org/10.13140/RG.2.2.10268.59528
Hello Eric Braid,
I have a little problem with your description. In the view of GRT the gravity wave is a process that has the curvature of space move. The same theory states that space expands. This means that at large enough separation points move away from each other with a speed that is unlimited by the speed of light. Space appears to be not limited to the speed of light. Light is limited in its speed through space.
Assume a single wave front coming from a sudden reduction of mass. Space was curved with one value and then suddenly the curvature is reduced. This reduction of mass is accompanied by the light that carries away the energy of that mass loss. Now this GW is a configuration of space curvature where the amount of space is stretched in different amount. This configuration moves with the speed of light. The light moves with the same speed. But the coordinates of space move with respect to space only a small amount.
This principle can be compared with cars in a traffic jam. The cars move slowly. Someone accelerates a little bit. The next behind reacts a little later. The one behind again a bit later. In this way the acceleration moves as a wave through the cars. The speed of that wave can be much faster than the speed of the cars. The space between the cars is the stretching of space. There is more space there. Light moves through space with a constant speed. If this wave moves with the same speed then one phase of the light wave will be always located at the same relative position to the moving GW.
Why would the GW move with the speed of light? The curvature of space at a moment only depends on the configuration of space that is at a light speed distance away. So because the past light cone defines the current curvature and the current curvature only can define the new curvature of those events that are at the future lightcone.
Regards,
Paul Gradenwitz
Paul Gradenwitz
Hi Paul
If Space is expanding then I assume it does so uniformly.
If this is the case, then are the marks on my rule and the distance between the wavelength nodes of EM radiation similarly expanding? I can't see any reason why this should not be.
So how can we measure this expansion and does it have any significance?
The expansion theory is based on measuring red-shift. How do we know this apparent red-shift is not caused by gravitational interaction with light or some contraction of the time dimension?
The alternatives are endless and our current state of technology leaves us simply making best guesses about which is a cause, which an effect and which measurements are simply failures in our understanding.
Ian
Hi Ian Proffitt ,
If space expands in large, as is assumed in the Lambda-CDM model, then it does it more or less uniform. A wave travels through the existing space. The first wave front travels through space and the next ravels a while behind. In the time the wave has reached the position where the pervious wavefront was space has added more of it. So the next wave front has to go a little longer till it reaches the position of the previous wave. Hence the wavelength will increase and we see redshift. The first wavefront has drifted with space a bit more than the second.
This is my rewording of the explanation of the cosmological redshift. This is an acceptable explanation why we would have cosmological redshift under the assumption that space expands. You are right that there are other alternatives. But explanations with tired light, gravity, all have their own characteristics. These make that it is possible to distinguish between them. Some of the options are ruled out because of that. I am sorry that I can't give you the exact documentation about that.
What remains is that there is a view that space expands. However the only information that is there is that the scale of the universe to the scale of the atom changes. Now you might remember that you have been in the kindergarten. Your memory of that time will give a large room. When you come back to that room as an adult you will notice that that room is much smaller than in your memory. For you it looks as if that room did shrink. This is because your measurement reference, the distance of your eyes to the ground, has changed. You did grow and that room stayed the same. Similar you can argue that not space did expand but that matter, the atoms, and with that the measurement ruler you use to measure distances, shrinks.
With the right parameter values you can describe all the cosmological observations based on shrinking matter and a constant universe. That is pure a matter of math. But in the end you need to explain why this is the case and then you need to find the explanation in a description of matter properties. If you assume that space expands then you need to explain the same scale change with a description of space properties. If matter shrinks then older matter did send out light with a larger wavelength. Because the younger matter is smaller it perceives the older light as redshifted.
Regards,
Paul Gradenwitz
Ian Proffitt: " If Space is expanding then I assume it does so uniformly. "
Hi Ian! I doesn't seem to be. If expansion can be taken as a measure of timeflow, and time runs fractionally faster in intergalactic voids than in galaxy-rich regions (converse of gravitational time dilation), then those voids will tend to expand slightly faster, giving us a positive feedback effect (a bit like when you over-inflate a bicycle inner tube, and the thinner regions "balloon" out). If the universe starts out with its massenergy fairly evenly distributed, the slightest variation in density causes the less-dense regions to expand faster, becoming even less dense, causing a lobed structure.
The surface of the resulting universe isn't so much like the pitted skin of an orange (dotted with little gravity-wells, regions where the surface has a slightly smaller distance from the centre due to gravitational time-dilation), it's more like the surface of a raspberry, a series of faster-expanding lobes or voids that tend to expel matter, with most matter pushed together into the "cracks" between the lobes by the uneven expansion.
Large-scale surveys of galaxy distributions do seem to show this sort of distribution, a series of interlinked voids, with galaxies concentrated in the walls between adjacent voids, or in filaments where typically three or more voids (or three or more intervoid walls) meet.
http://www.2dfgrs.net/
It seems to be essentially an irregular foam-like structure.
While the "foamy" structure can be explained by differential positive-feedback expansion, other attempts to explain it have run into trouble. One of the big problems is that it takes so long for light to cross a void, that nobody seems to understand how a void can self-regulate to have such uniformity across its walls. If you think of the walls as being the primary structures, it doesn't seem to work. How does a wall communicate with its opposing wall? However, if the voids are the primary structures, and are expanding, things seem to be easier to explain.
Other than the void structure, the second prediction associated with differential expansion would be that we would be allowed to see isolated stars in the middle of deep voids whose age appears to be greater than the assumed age of the universe. This would be because more cosmological time has elapsed for matter in a deep void than it has for most of the universe's inhabitants, who wil ltend to be living in "galaxy wall" regions.
Eric Baird
Eric the link you posted was very helpful, thank you.
I now need to do some in-depth studying.
Based on a quick perusal and on your commentary above it would appear that gravity is implicated in controlling or slowing down of the expansion of the universe and this is evidenced by variations in red-shift between 'populated' and sparse regions of space.
My understanding of the nature of expansion is that it is space that is expanding from a smaller to a larger volume, not the contents simply spreading out in an infinite but pre-existing volume.
The concept that it does so in a haphazard fashion based on the contents of the volume is entirely new to me.
So my next question, when I have done some reading, will be along the lines of "Does matter / gravity interact with light or is it somehow altering the progression of time where there is large scale and dense mass?"
Ian
Hello Eric Baird ,
You state that the voids control the structure of the universe. Now you could think that the emptiness of the voids pushes the matter to the side. The less matter there is on a location the higher the zero point energy can be there. There is no matter, a border condition, that limits certain modes, frequencies of energy. Taking the that quantum mechanics predict an energy density that is 10120 higher than the GRT predicts you could use that as a gravity push. A gravity push by the ZPE would move its effects with light speed. Because the energy density in the vicinity of matter has to be lower the observed speed of stars in galaxies does not need Dark Matter but to remain together but only the less matter, gas, is around the higher gravity effect are. What do you think of such view?
Regards,
Paul Gradenwitz
Hi Eric Baird,
EB: So suppose that we have an oscillating piston, whose velocities and accelerations create lightspeed anisotropies, first in one direction and then in the other, and these changes propagate away from the end of the piston as gravitational waves, alternately increasing and decreasing the velocity of light as defined along the piston axis w.r.t. background.
That is not the nature of GR waves, they are quadrupole, transverse.
If the piston produces wavefronts moving in a direction we call the z axis, then the speed of light will be increased along the x axis while being decreased along the y axis during one half-cycle and that wavefront moves in the z direction at a uniform speed of c that isn't affected. During the next half-cycle, the effects on x and y are the opposite.
There are good animations here:
http://www.einstein-online.info/spotlights/gw_waves.html
Just under the third animation you will read:
- "The animation also illustrates a more general property of simple gravitational waves. As you can see, in the direction of the wave's propagation, the separation between particles does not change. In this particular animation, the wave travels from right to left, and in mapping the change in particle distances caused by the gravitational wave, we only have to shift particles upward or downward, toward us or away from us, but not sideways. Simple gravitational waves only squeeze and stretch space in directions perpendicular to the direction of their propagation. In the language of physics, such waves are called transversal."
Hi Ian,
IP: The concept that it does so in a haphazard fashion based on the contents of the volume is entirely new to me.
This is fairly well known, the effect of gravity from the contents (other than 'dark energy') is to slow the expansion but the rate of slowing depends on the mean density. The Milky Way is in a large region known as the KBC Void which is about 30% less dense than the universe as a whole. That is though to explain why local measurements of the Hubble Constant are around 72 km/s per Mpc while Planck's value based mainly on the CMB is 68 km/s per Mpc.
Hello all, this discussion topic is as stated, on a specific logical fallacy in GR, not a general speculation on GR. I would like to ask to stay on this theme, here, and avoid off-topic replies. A review of the most important points in the discussion was added, in the main text of the discussion itself, under NOTES. Some points were omitted, for brevity, but are represented in the replies above.
Hello all: The original reference by Minkowsky on spacetime, the current common basis of SR and GR, began with, "Henceforth, space for itself, and time for itself shall completely reduce to a mere shadow, and only some sort of union of the two shall preserve independence." [1], 120 years ago.
Cheers, Ed Gerck
[1] http://rgs.vniims.ru/books/spacetime.pdf
Hi Ed, From your notes:
EG: a. To consider superluminal effects in gravity is a bet that gravity as that wave can escape from colliding black holes, and reach distant Earth, an experimental fact maybe measured by LIGO, ahead of the detection time considered by LIGO themselves, of conventional gravity waves modeled by a spacetime curvature.
Conventional waves are emitted as a result of the orbiting of the binary system and are generated at a distance greater than the binary system so do not escape from the black holes, they are created far outside.
EG: b. We are NOT talking about conventional gravity waves, a curvature in spacetime (see discussion theme, above), where gravity waves must follow the speed of light in vacuum, by construction.
Theory says they move a little slower than light at very high amplitude but at the speed of light for any practical amplitude. Those are the quadrupole waves that have been observed and it has been confirmed that they do move at c in accordance with GR.
Now in nature a wave is a wave and has one speed in any given medium for any given format so if you are talking about quadrupole (tensor) waves, their speed is c as confirmed by observation. If you want to have waves moving at a different speed, they must also be of a different format, for example transverse 'S' and longitudinal 'P' seismic waves travel at different speeds because of their different format.
You comments on "c=1" are somewhat irrelevant, c is nothing more than a constant for converting units like 25.4 for converting inches to millimetres.
Hello George Dishman , Experimetal effects are not the topic here. This is not about conventional waves. This thread is about a logical fallacy in GR -- does it exist or not? Please use the space here for this topic.
My comment on c=1 is correct and self-evident, and c is not what you say. Please do not raise false controversies for traffic-sake.
There is no fallacy.
The experimental data is crucial because it proves that the waves exist in nature and move at the same speed as gamma rays. If an alternative theory (i.e. "not about conventional waves") predicted a different speed then it would be falsified by the observation unless it predicted both the conventional speed for the quadrupole format and an additional format that moved at a different speed. The preliminary results from LIGO are unfavourable for both scalar and vector forms but that test is tentative at present, it will only become robust with a statistically significant number of detections.
EG: My comment on c=1 is correct and self-evident, and c is not what you say. Please do not raise false controversies for traffic-sake.
What I said is not controversial in the slightest, if you state the speed of light in miles per hour, it has a different value from the value in metres per second, that is self-evident. If you state it in light-seconds per second, it has the value 1 and that is what theoretical scientists always do, they don't care about units.
Hello George Dishman , Please do not raise false controversies. No one is disputing the primary importance of experiments in physics. Most physicists will consider experiment first. You wrote, "... c is nothing more than a constant for converting units like 25.4 for converting inches to millimetres."
This is false, c is clearly not a conversion of the same dimension, like inches to mm. This is a false controversy, and RG space and time of researchers should not be used to ask or reply to such pseudo comments, false science.
This discussion is about a logical fallacy in GR. It is NOT about any experiment, but the theory that represents nature. SR is powerless to define it, or any experiment. If you do not wish to stay in the theme, which is the discussion here, please observe or leave. You can also create your own discussion in RG, no one is blocking.
Please help us keep this discussion focused on the logic of the formulation. Your arguments are impotent to reach that, and we would like to stay on topic. Life is a school, if you do not stop, this question may suffer. It is not helping the group of this discussion, and no thread should be hijacked, not yours either. Let's keep RG useful for all.
Ed, what I am saying is entirely pertinent to your question but I'm happy to leave the thread alone. I am just saying that you are only going to waste your own time by burying your head in the sand and ignoring the observational evidence that gravitational waves travel at the same speed as a gamma ray burst because any alternative theory of gravity is now going to have to be deigned to comply with that fact. That is how experimental science constrains the theoretical.
George, I think it is the other way around. Trustworthy mathematics restricts all experiments. Quaternionic field theory does not tolerate fields to obey incorrect field equations. See:
BehaviorOfBasicFields; http://dx.doi.org/10.13140/RG.2.2.15517.20960
Fields must obey the same mathematical differential equations. However they may differ in start and boundary conditions. That causes the difference between electromagnetic field behavior and gravitation field behavior.
Hello Hans van Leunen : Your answer, though it may be useful, is off-topic here. We are not discussing anyone's theory but what is proposed above. Namely, this thread is about a logical fallacy in GR -- does it exist or not? Please use the space here for this topic. It is narrowly defined on purpose and utility.
Hello all: We added NOTE (g) in the discussion itself, above:
g. Off this discussion topic. but may be worth mentioning here. This is not a conceptual choice only, but must be also experimental, which one could then call natural, it is in nature. Reality, experimentally, must be at least 4D as in spacetime, it “does not fit” inside 3D in all cases. This is not 3+1, it is 4, integrated, you cannot separate. Now, this does not mean that reality cannot be >4 in dimensions, and exceed c in that context, of 8D or more... Gravity may be modeled in higher dimension than four, then. This is, today, speculative, but it is useful to know that v > c is not forbidden for gravity by SR, considering this discussion.
Cheers, Ed Gerck
Ed, this is exactly my criticism. You appear not to wish to obey the correct mathematics and you do not start from a trusted modelling platform.
Gravity waves are ordinary field behavior. The only way you can get superluminal is by expanding the field and let the wave travel during a sufficiently large period. This can be comprehended without GR.
Relativity only gets involved when observers receive their information when it is transported through a field. In this case it is the same field that transmits the gravitation wave.
A simple wave equation can already explain the fronts of the gravitation wave and how the universe gets expanded.
If the universe expands, then the Lorentz transform is no longer a reliable descriptor.
Hello Eric Baird , Ian Proffitt , Paul Gradenwitz , and Stefano Quattrini : The currently top-voted answer in this thread is off-topic. Experimental effects are not the topic here. This is not about conventional waves either. This thread is about a logical fallacy in GR -- does it exist or not? Please help us keep this discussion focused on the logic of the formulation of GR.
Your arguments and/or recommendations are impotent to reach that, and we would like to stay on topic. It is not helping the group of this discussion, and no thread should be hijacked, not yours either. Let's keep RG useful for all.
Hi Hans,
HvL: George, I think it is the other way around. Trustworthy mathematics restricts all experiments. Quaternionic field theory does not tolerate fields to obey incorrect field equations.
I agree, theories must be mathematically self-consistent, but maths that predicts incorrect outcomes is not representing reality, which is the aim of physics.
A simple example is Newtonian physics versus SR. Both the Galilean Transforms and the Lorentz Transforms are fully self-consistent mathematically and the former gave us a great deal of physics over ~250 years but in certain experiments towards the end of the 19th century, some experiments were showing that it wasn't quite right. Changing to the Lorentz Transforms solved many of those.
If quaternionic field theory for example gave different predictions from what is observed, we would conclude that while it might be fully self-consistent, it isn't the right maths to use for what we are modelling. I'm not saying that is the case, but what I am saying to answer Ed's question is that any future alternative to GR must accurately model the observations by LIGO, and that means it must have a wave solution that propagates at the same speed as EM, because the gravitational waves were observed within 2 seconds prior to the gamma burst arriving after having travelled for 130 million years.
Hello Ed,
Regarding whether this is on-topic or not, the title and first paragraph of your question state:
- "On the existence of gravity waves with superluminal speed .. or any value. This is forbidden by current general relativity theory, that defined the speed of gravitational waves to be .. the speed of light in vacuum. However, we conjecture that gravity waves, using a different formulation of gravity, not using the curvature of spacetime to represent gravity, could allow such results to be calculated."
What I am saying is that observation refutes that claim for any potentially valid theory. A "different formulation of gravity" must still predict "the speed of gravitational waves to be .. the speed of light in vacuum" so I consider this directly addressing your question.
I hadn't intended to reply again Ed, but Hans directed his comment at me.
Special relativity already plays at the location and the instant of the observed event when a difference exist between the observed event and the observer. Also in that situation the embedding field transports the information from the event to the observer. Simple mathematics then shows that the Lorentz transform describes the involved coordinate transformation from the Euclidean format in which physical reality presents its data to the spacetime format in which the observers perceive. Also in flat space the same hyperbolic coordinate conversion that introduces time dilation and length conversion takes place. Any deformation of the embedding field influences the information path and enforces the application of tensor calculus to understand the effect of the differential calculus that controls the behavior of the field at the situation of the observed event. Thus the differential calculus is the primary descriptor of the dynamics of the field. Next the Lorentz transform and tensor calculus help to compute what the observer will perceive. If GR draws the wrong conclusion, then either it applies the wrong differential calculus or it implements the Lorentz transform or tensor calculus in the wrong way. One of the ingredients is that the universe continuously expands. This already explains that in otherwise flat space a moving front in the embedding field can be observed to move with superluminal speed. In this situation tensor calculus plays no role.
Hello all, In the interest of focusing the attention, let us recall that this discussion is about a logical fallacy in GR. It is NOT about any experiment, but the theory that represents nature. SR is powerless to define it, or any experiment.
It is not against experiments either, the purpose of physics. That would be a false controversy. It is about experimental data that is missed in the current model -- it is about noise vs. signal, they are essentially the same! What might be noise for one, might be signal for someone else. Thus, contemplating the possibly is useful, and noting that it is experimentally possible.
And this has an inverse relation to what is seen experimentally today, that what we do not measure is, maybe, possible. I don't have to recall here the many cases where this happened before in science, and there are many examples in QM, today's perceived "bane" of SR and GR.
Hello all: We are, ultimately as a goal, preparing the field to discuss the possibility of QM effects, or others, on the formulation of gravity, and how they would NOT be forbidden by SR or GR. This discussion here, which is based on logic, can free the logical mind of such concerns.
Hello Zbigniew Motyka
, The limitation of c=1 comes from SR, not GR. Therefore, it is powerless to limit GR. We could add other dimensions x to SR, for example, and this could allow GR spacetime-x to "bend" in different ways. The discussion points out that GR is not limited by spacetime or SR.
Hello Ari Ben-Judah
: Thank you for your quote, but In the interest of focusing the attention, this discussion is about a logical fallacy in GR. It is NOT about any theory, NO experiment, but the GR theory that represents nature. SR is powerless to define it, or any experiment.
Hello all: This thread arrived, in the past, at a conclusion, which is stated in the body of the initial text. There is no room to refuse to notice an obvious thing, an error in logic, or to re-explain here; the reasoning and references are available above, to anyone.
We are now ready to move to non-mathematical and non-physical aspects. We are talking about the historical and intersubjective aspects, which are important to us qua humans. Finding a humanly acceptable answer is difficult in physics or maths today, and, pretty soon, in all natural sciences. Therefore, this very thread is important.
We suggest, as in physics, that facts are what you were willing to bbelieve. A bias, preventing a more complete vision. That is another motivation here, to abandon bias. It has no place going forward, and may prevent us from seeing what is plain to see.
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