Too much attention is given to ambiguous expressions, that reflect historical, rather than logical content.

The correct formulation, now, is known and much simpler.

Matter couples to the gravitational field through its energy-momentum tendor, only, because that term is the only term consistent with invariance under gfneral coordinate transformations. The only iwdue is whether the geometry of spzcetime is determined by the metric, onlj,’or by other fields, that can’t be identified as matter fields, because their energy-momentum tensor doesn’t have the correct positivity properties.

At any given point in spacetime, it’s possible to choose coordinates, such as to make the metric flat. If, however, there do exist scalar, spinor or vector fields, that define the spacetime geometry (as happens with scalar-tensor theories or supergravity) it’s not, in general, possible to make the scalar fields vanish, as well, at sny given point.

And the statement that spacetime isn’t flat, simply, means, that such a transformation isn’t globally defined.

Gravitons can’t be individually resolved, so it doesn’t make sense mentioning them.

Macroscopic acceleration is due to EM fields whereas gravitation is due to the geometrical deformation of the potential surrounding any mass (in the case of Newton the source is a point with mass M). So the effect might be comparable but the phenomena are distinct.

JES

I would like to assume that gravitons do exist. If so, would I be correct so say that they convey changes in acceration, or changes in gravitational field strength, or changes in the metric? I think this would be the third derivative of positon, sometimes called jolt. As comparison, what change in the electric field do photons convey, electric field strength?

John A. Macken,

The strong equivalence principle is always valid,either you like it or you do not like it.

Issam Mohanna, Riccardo C. Storti Please explain your answer more completely. Specifically address my example of assuming gravitons cause gravity and gravitons not causing physical acceleration. Suppose the spin of gravitons could be detected. Then it would be possible to do an experiment in a closed room to tell the difference between being in a gravitational field (lots of gravitons) or being in an accelerating spaceship (no gravitons).

Lets put it this way.

If found invalid would elicit quite a scandal and uproar, gravitons or not.

John A. Macken,

Your last comment is a clear proof of your lack of understanding of what the strong equivalence principle,defined in the description of this thread ,is all about.

Juan, Riccardo and Issam. I honestly am trying to understand how you can equate gravitational acceleration cause by the exchange of graviton messenger particles and acceleration caused by the conservation of momentum. A spaceship achieves acceleration by using the electromagnetic force to accelerate and expel rocket exhaust gas. Energy is expended to physically accelerate both the spaceship and the exhaust gas.

A closed room, stationary on the surface of a planet, can have the same magnitude of acceleration, but this is gravitational acceleration, not physical acceleration. There is no energy being expended to accelerate rocket exhaust or other matter.

There is doubt whether gravitons exist, but for purposes of discussion, I postulated gravitons transfer the gravitational force. My point is that if gravity is transferred by gravitons and if gravitons are detectable, then it would be possible to do an experiment that invalidates the strong equivalence principle. Gravitons would be detected when the room is in a gravitational field and gravitons would not be detected when the acceleration is the result of rocket acceleration.

The weak equivalence principle implies that gravitational mass and inertial mass are the same. I see no reason why the weak equivalence principle must be wrong if the strong equivalence principle is invalid.

Strong Equivalence is INVALID. Gravity involves tidal forces - those as if from a central point. The direction of force in a rocket would be along its axis. In gravity the force is not parallel from one side of a rocket to the other. The issue is one of measurement ability.

Physics never claimed that gravity is transferred by gravitons. Gravitons are particles associated with gravitational waves which travel at speed of light. But action of gravity is instantaneous. If gravitons were to transfer gravity then gravitational force would travel at the speed of light which is absurd. Gravitational waves are supposed to be the perturbations in space time fabric. They do not transfer gravitational force. It is the space time fabric that instantaneously transfers the gravitational force. Perturbations in space time fabric also causes perturbations in gravitational force. Gravitational waves are discovered but the graviton is not discovered. Question of validity of strong equivalence principle does not arise.

Vikram Zaveri Most physicists believe gravity is transferred by gravitons, but there are also other possibilities. I personally believe another explanation, but the question I pose can be illustrated by assuming gravitons. However, it is well established that gravity propagates at the speed of light, not instantaneously as Newton assumed.

I am contending that only if gravity is a purely geometric effect can the strong equivalence principle be correct. The weak equivalence principle is well established but this does not prove or disprove the strong equivalence principle.

Riccardo C. Storti I admit that I cannot quote a survey about the percentage of physicists that believe gravitons transfer gravity. I formed this impression, but I attempted to check with a Google search of "Is gravity caused by gravitons?" Part of the answer stated, "Most theorists believe that gravitons must exist, because quantum theory has successfully explained every other force of nature." This is not proof of a majority, but gravitons must be the #2 most common belief if it is not #1.

Dear John A. Macken ,

there is a non trivial diatribe going on about the principle of equivalence.

I guess first we should try to get the relevant definitions then we can discuss.

EP = principle of equivalence initially formulated by Einstein

as a physical equivalence between acceleration and static gravitation

or a local equivalence between free falling and inertial frame of reference:

in other words, the effects of gravitation are locally indistinguishable from the effects of acceleration.

NEP = Newton Equivalence principle basically EOTOVS: Fi=Fg equilibrium balance which is the first one measured by the pendulum by Newton

UFF = universality of free fall (Galilei)

WEP = Weak Equivalence Principle = NEP + UFF

EEP = Einstein Equivalence Principle = WEP + LLI + LPI (Dicke formulation)

• where LLI = Local Lorentz Invariance, and where Lorentz Invariance is SR,
• LPI is the local position invariance which is Gravitational time dilation and Gravitational redshift.

SEP = Strong Equivalence Principle which should involve EEP and ?

Riccardo C. Storti General relativity (GR) gives equations that describe the macroscopic properties of gravity. However, GR does not describe the underlying physics of how a fundamental particle causes the curvature of spacetime or how this results in a force. It was necessary for Einstein to postulate the equivalence of gravitational and inertial mass because GR does not prove this. A discussion of the validity of the strong and weak equivalence principle goes beyond GR. Gravitons postulate a mechanism for the transfer of gravitational force at a distance. If a mass is prevented from following the geodesic, a real force is exerted on the mass. The strong equivalence principle brackets the possible explanations.

Dear all,

1) There is no proof of a delayed potential in the gravitational interaction!

There are two possible explanations:

The interaction is immediate or, all masses are surrounded by a medium giving the gravitational interaction.

2) The gravitational waves extend with light velocity!

We conclude: All masses are surrounded by a medium where any disturbance is extending with the light speed.

JES

There are at least 4 types of mass:

1) inertial in F=ma,

2) energy E=m^2 released in annihilation,

3) gravitational in F~Mm/r^2,

4) de Broglie clock hf = mc^2 (confirmed for electron: Article A Search for the de Broglie Particle Internal Clock by Means...

Equivalence between 1) and 2) comes from special relativity.

For gravitational mass we don't even know about electron - there was 1965 experiment suggesting zero mass, but it has subtle problem and it seems we still don't know: https://indico.cern.ch/event/361413/contributions/1776296/attachments/1137816/1628821/WAG2015.pdf

We don't know much about the clock, e.g. if all particles have it?

Jarek Duda You raise an interesting point about four ways of defining mass. In particular, the mass from the de Broglie clock frequency (zitterbewegung) brings up another reason to doubt the strong equivalence principle. The strong equivalence principle only works if the assumption is made that the gravitational force is caused by the geometry of space without explaining how matter/energy causes the curvature of spacetime. If a particle causes the surrounding space to curve by generating gravitons or standing waves, then gravitational force and inertial pseudo-force can be related without incorporating the exact same physics.

You conclude with the statement: "We don't know much about the clock, e.g. if all particles have it?" I will briefly comment on this statement. The wave-based model of the universe I propose (see the link below) models a fundamental particle such as an electron as a stable rotating wave (a soliton). All fermions in this model have the same displacement amplitude (Planck length Lp) and the same angular momentum (ħ/2). They have different rotational frequencies (different clock frequencies), a different Compton wavelength (ƛc = ħ/mc ). This model generates an electron's energy, inertia, gravity and electric charge (if the fine structure constant is assumed). This model makes several predictions about the properties of an electron. Two of the simplest predictions are reduced to the equations below.

rg = Lp2/ƛc (Equation 1)

RG/Re = α-1(Lp/ƛc)2 (Equation 2)

Equations (1 and 2) use an electron's wave properties (Lp and ƛc) to generate an electron's gravitational radius (re) and the ratio of the forces between two electrons. In Eq. (2) RG/Re is the ratio of the gravitational force magnitude between two electrons divided by the electrostatic force magnitude between these same two electrons.

www.researchgate.net/publication/353049276

John A. Macken, experimentally ~10^21 Hz the clock was tested only for electron - in simulations of Dirac equation ( https://en.wikipedia.org/wiki/Zitterbewegung#Experimental_simulation ) and directly in the famous "A Search for the de Broglie Particle Internal Clock by Means of Electron Channeling" 2008 paper. This important experiments should be recreated, Marc Fleury says he would like to do it with Batelaan. It is nontrivial, needs ~80MeV electron beam.

Such clock is also hypothesized for other particles, mass ( https://en.wikipedia.org/wiki/Matter_wave ), however, there there are many issues, like ~ 10^24 Hz enormous frequencies, their addition when grouping masses ...

Electron/positron clock is the most crucial, I am agnostic about the rest in this moment. It would create coupled pilot waves like in hydrodynamical QM analogs (gathered: https://www.dropbox.com/s/kxvvhj0cnl1iqxr/Couder.pdf ).

Jarek Duda

In following theory, the gravitational mass is equal to relativistic mass. It works fine with the photon. In general relativity (GR) gravitational redshift is not invariant and there is no derivation for it. In periodic relativity gravitational redshift is invariant and is derived using a term called de Broglie force which is ignored by GR.

Periodic relativity: gravitation within electromagnetic wave

https://www.researchgate.net/publication/355095851_Periodic_relativity_gravitation_within_electromagnetic_wave

Periodic relativity is based on the concept that time is periodic in nature and hence all particles have their own internal clock.

John A. Macken,

“The strong equivalence principle only works if the assumption is made that the gravitational force is caused by the geometry of space without explaining how matter/energy causes the curvature of spacetime.”

The shortcoming of GR described in your statement is amended in periodic relativity (PR) by introducing all pervasive infinite indivisible motionless fundamental substance of the universe which is neither matter nor energy, but all matter/energy is created from it when it begins to move. In short, space-time fabric of GR is replaced by this indivisible fundamental substance which develops stress within itself called gravity because of its indivisibility. When this indivisible substance is apparently divided into particles, the gravity comes into picture which tries to oppose the motion of the particles and restore their motionless state.

Five days ago John Macken commented that there is no proof that a rest mass carrying particle curves space. There are a couple of arguments/observations that show that John Macken is right.

Gravity is an emergent force field because without rest mass (matter) there is no force of gravity (Einsteins lecture at the Leiden university in 1920). Eric Verlinde proved that Newtonian gravity is an emergent force field too (2011). The consequence is that the force of gravity has no basic quantum field of its own. That means that gravity cannot have a dedicated intermediating particle (the “graviton”).

If space is forced to curve by the creation/existence of a rest mass carrying particle we have to prove that the transition of local mass into local rest mass results into the expansion of the volume of the local mass.

If we apply energy to a mass/rest mass carrying particle, it accelerates. Thus if we apply a large amount of energy to a rest mass carrying particle the velocity of the particle nears the speed of light. But the particle itself doesn’t expand its size.

There are no measurements that confirm that energy “blows up” the size of accelerating particles. The consequence is that energy is not equivalent with volume. A conclusion that is in line with Einstein’s famous equation E = m c2 (energy is restricted to the change of surface area within the structure of the involved fields).

The creation of rest mass is thought to be the transfer of energy from a decreased scalar to the local electric field (the local concentration of energy we have termed mass). But this is a local transformation of energy that is conserved. That means that the decrease of energy of the scalar results in the increase of the local electromagnetic field and visa versa. Einstein’s concept means the creation of local energy “out of nothing” (a violation of the law of conservation of energy). That is why in quantum field theory there exists no accepted model that describes how the Higgs mechanism can locally “blows up” space itself (the field structure). Moreover, in QFT time is a constant. The model of spacetime don't exist in QFT.

Now the question if accelerating matter creates a force field that is equal to the force of gravity.

Gravity emerges at the moment that rest mass is created. Thus as long as the rest mass exists, there is a corresponding gravitational force field that surrounds the rest mass. If I sit in a racing car and I push the accelerator pedal I will be pushed against my seat. At the moment the accelerating stops, the push is over. Now the question is if accelerating a racing car is equivalent to the influence of the force of gravity. I suppose that not everyone will agree. Thus what is equivalence between the influence of accelerating and the influence of gravitation? The answer is simple, the equivalence is limited to the continuity of both influences.

Now “freefall”. The cause behind the force of gravitation is the rest mass of the particle (the released energy by the decreased scalar of the Higgs field). Thus if we have 100 rest mass carrying particles together, we have 100 equal sources of gravitation (the gravitational force that surrrounds the particle).

If I drop 2 objects far above the surface area of the moon and 1 object is a configuration of 100 rest mass carrying particles and the other object is just 1 rest mass carrying particle, the gravitational force on each rest mass carrying particle by the moon is the same. Thus the configuration of 100 particles is “falling” to the surface area of the moon with the same velocity as the single rest mass carrying particle. In practice there are no objects that represent single rest mass carrying particles, so the experiment is done with the help of neutral atoms that represent a number of rest mass carrying particles that fall in the direction of the moon. Like they did during the Apollo landings on the moon (a hamer and a feather).

With kind regards, Sydney

You should be aware that the famous law E=mc^2, is not from Einstein!

It was proposed by at least 2 other scientists before Einstein.

JES

Here is how to calculte g (acceleration of gravity)of the earth.

mg= GMm/(RR)

R radius of earth

m drops out

g=GM/(RR)

M mass of earth.

Same calc. for moon or any other planet.

Cannot really imagine the gravitons here.

Note g takes the place of a in F=ma, that is why "acceleration"

Undoubtedly,Albert Einstein was the first who found the correct relation or equation that relates mass and energy.Other scientists tried to find it but they failed.

It's enough to have studied at the McDonald burger academy to acknowledge that the statement...

"The Strong Equivalence Principle of Gravitation states that the effects of acceleration are indistinguishable from those of gravitation"

...is brain-dead nonsense ! Every child can see and understand that !!

I initiated a similar discussion based on a new thought experiment which results in a different curvature (bending) of light. I tried to show Equivalence Principle is as baseless as any metaphysical endeavour.

Preprint A New Equivalence Principle with a Different Curvature of Light

Please see comments under the mentioned discussion

https://www.researchgate.net/post/What_is_the_real_shape_of_the_gravitational_bending_of_light?_ec=topicPostOverviewAuthoredQuestions&_sg=9WUn27cfhBP3D7xGWZN8QVNyii_UO4ull9GP3GYHX03oosk6JJBgn4UgckyUUmqnoxfJgNPNxVq0pXrK

Ziaedin Shafiei

Yes, the Faraday Pradoxor the ``moving magnet and conductor problem'' is one of the motivations of Special Relativity. Preprint Replacing Special Relativity