The Many Faces of Gravity

We show that the number of different gravitational effects is significantly greater than previously thought. First of all, it turned out that the observed constancy of the speed of light relative to the surrounding masses is a special case of a previously unknown fundamental gravitational effect related to the action of gravitation on the speed of light. In other words, the constancy of the speed of light becomes an integral part of gravitation. Moreover, it turned out that the increase in inertial mass and the dilation of the proper time of particles that were accelerated relative to the surrounding masses are also consequences of this fundamental gravitational effect. All of these secondary effects are in the same row with such well-known effects as gravitational refraction and gravitational lensing, which are also a consequence of the action of gravitation on the speed of light. Their belonging to gravitation causes a number of unique features, for example, asymmetry in time dilation and anisotropy of the speed of light, which have been successfully confirmed experi-mentally. The research is based on a detailed analysis of a large set of experimental data using the classical axiomatic approach. the energy. refraction


Introduction
All terrestrial experiments on measuring the speed of light in vacuum show the constancy of the local speed of light relative to the Earth. An example of such an experiment is the measurement of the speed of light emitted by accelerated particles. It is clearly seen here that the speed of the emitted light remains constant relative to the Earth and does not add up to the speed of the emitting particles.
The results of this experiment are fully consistent with special relativity. It should be noted that the measurement of the speed of light in this experiment was per-ence of these artificial satellites, which is considered to be inertial in a small local area, the local speed of light should be constant relative to the satellites. However, contrary to expectations, the measured speed of light is still constant relative to the Earth and significantly anisotropic, that is, not constant relative to the satellites themselves. This means that the local speed of light on our planet is always constant relative to our planet, regardless of the choice of the frame of ref- erence. This completely unexpected result is an important turning point that initiates the search for new approaches to relativity and gravitation.

Initial Physical Assumptions
A remote observer can indirectly observe a decrease in the effective speed of light in the gravitational field of the Sun as a certain delay in the return of the electromagnetic radiation [2]. Taking into account this experimental fact and numerous experimental data that the local speed of light on our planet is constant relative to our planet (see Section 1), we assume the existence of a fundamental gravitational effect that establishes a certain allowed speed of light relative to the source gravitation: where r is the distance to mass M, c is the speed of light at an infinite distance, and G is the gravitational constant. This gravitational effect explains the observed constancy of the local speed of light on Earth, as well as other experimental facts that will be considered later, but it explains only half of the delay of the electromagnetic radiation in the gravitational field of the Sun. To explain the second half of the delay, we are forced to assume the existence of a second fundamental gravitational effect that shortens the local length in space around the source of gravitation: where L is the unit of length at an infinite distance. Shortening the local unit of length L′ leads to some increase in the total number of units of length on the trajectory of light ( Figure 1).
Due to the lengthening of the trajectory, the remotely observed effective speed of light becomes equal to ( ) Thus, the delay of electromagnetic radiation observed in the gravitational field of the Sun is a secondary gravitational effect, which is formed by the fundamental gravitational effect of the allowed speed of light and the fundamental gravitational effect of shortening the local length.
R. Sadykov Journal of High Energy Physics, Gravitation and Cosmology

Gravitational Refraction
Due to the variable effective speed of light c′′ caused by the two fundamental gravitational effects (see Section 2), the gravitational field of central mass M acts as a refracting medium with a variable index of refraction: The angle of refraction of light in weak gravitational fields, for example, in the gravitational field of the Sun ( Figure 2) is equal to where r is the minimal distance of the light ray from the center of mass M. This angle is two times greater than the Newtonian value for the deflection of light. Thus, the gravitational refraction is a secondary gravitational effect, which is formed by the fundamental gravitational effect of the allowed speed of light and the fundamental gravitational effect of shortening the local length. Gravitational lensing, in turn, is a consequence of gravitational refraction and therefore can be classified as a tertiary gravitational effect.

Gravitational Attraction
Consider the following physical model. Inside an ideal reflecting sphere, a large number of photons move in different directions forming a spherical photon clus-Journal of High Energy Physics, Gravitation and Cosmology ter. The total kinetic energy of photons forms the internal energy of this cluster E. In addition to internal energy, the photon cluster is also characterized by an effective inertial mass: Due to the large number of photons and their numerous reflections, this cluster can be viewed as a modified light clock. Thus, the photon cluster as a physical model can simulate the energy, inertial, and temporal properties particles with a non-zero inertial mass. This allows the cluster to act as a test mass.
Let the photon cluster be located in the gravitational field of the central mass M (Figure 3). Gravitational refraction violates the initial dynamics of photons forming the cluster, which leads to acceleration of the cluster in the direction of mass M, that is, the gravitational attraction arising under these conditions is a direct consequence of gravitational refraction.   Thus, the gravitational attraction accelerating a photon cluster or any test particle to the central mass is a tertiary gravitational effect based on the fundamental gravitational effect of the allowed speed of light and the fundamental gravitational effect of shortening the local length. Identical gravitational acceleration of various particles [3] under the same initial conditions means that the internal energy of these particles, as in the case of the photon cluster, is contained in the form of kinetic energy. In other words, any potential energy, including the internal energy of particles, is a latent form of kinetic energy.

Gravitational Time Dilation
Let the remote observer located at point A ( Figure 6). The photon cluster moves from point A to point B located on the surface of the central mass M. A decrease in the allowed speed of photons c′ relative to the central mass M (see Section 2) leads to an increase in the period between reflections of photons, which can be considered as a dilation of the proper time of the cluster: The same thing happens with an ordinary light clock after moving from point A to point B.

Gravitational Energy
The internal energy of the photon cluster consists of the kinetic energy of photons that form the cluster (see Section 4). Gravitational acceleration of the photon cluster (Figure 3) is accompanied by the transformation of the internal energy of the cluster into the external kinetic energy. Gravitational refraction initiates R. Sadykov Journal of High Energy Physics, Gravitation and Cosmology this transformation, but like any other refraction does not change the total energy of the system. As a result, the internal energy of the cluster decreases: but the total energy remains constant. This conclusion obtained for the photon cluster can be extended to any test particle with a nonzero inertial mass due to their inertial, energy, temporal, and gravitational equivalence (see Section 4).
Thus, contrary to expectations, the gravitational energy is not contained in the gravitational field. Instead, gravitation uses the internal energy of the test particle to gravitational acceleration this particle.
Given the properties of gravitation discussed above, the remote observer lo-

Two Different Forms of Gravitational Time Dilation
The gravitational effect of the allowed speed of light dilates the proper time of the light clock T ′ at point B ( Figure 6) by decreasing the allowed speed of light c′ relative to the central mass M (see Section 5). When the same light clock accelerates to speed υ′ , this gravitational effect still maintains the allowed speed of light c′ relative to the central mass, which increases the period of passage of the photon between the mirrors of the light clock (Figure 7).
Thus, time dilation is a consequence of the fundamental gravitational effect of the allowed speed of light and is realized in two slightly different forms: the first form T ′ appears when the test particle is placed in the vicinity of the source of gravitation; the second form T ′′ arises when the test particle moves relative to the source of gravitation. Both forms of time dilation take place on the satellites of the Global Positioning System [4].

Propagation of Light in a Moving Medium
Let the remote observer located at point A ( Figure 6). The transparent cube moves at a speed of υ′ in the vicinity of the central mass M. By condition, the speed υ′ is much less than the allowed speed of light c′ in this local area.
The photon moves inside the transparent cube in the same direction as the cube.
where 1 c is the average speed of the photon when the speed of the cube is zero. This result, known as the partial dragging of light, was observed in the water flow in the Fizeau experiment [5]. Thus, the Fizeau optical experiment is another convincing proof of the existence of the allowed speed effect.

Feature of Gravitation in Interstellar Space
Consider the following physical model. The photon moves from remote point A to point B located in the central hollow area of the spherically symmetric mass M (Figure 8). In the process, the fundamental gravitational effect of the allowed speed of light gradually decreases the allowed speed of the photon c′ (see Section 2). In addition to this, the fundamental gravitational effect of shortening the local length reduces the effective speed of the photon c′′ (see Section 2). This speed reaches a minimum in the empty central area (see Diagram in Figure 8).
Mass M from this area can be considered as some system of surrounding masses.
One of several secondary gravitational effects-gravitational refraction (see Sec-R. Sadykov Journal of High Energy Physics, Gravitation and Cosmology tion 3) is completely absent here due to the constant effective speed of light c′′ in the entire central area. The absence of gravitational refraction, in turn, leads to the absence of tertiary gravitational effects-gravitational lensing and gravitational attraction (see Sections 3 and 4). However, other derivative gravitational effects and two fundamental gravitational effects continue to act. In particular, the internal energy of the test particle E (see Section 6) moved from point A to the central area decreases to a value of E′ (see Diagram in Figure 8). Parallel to this, the proper time of the test particle T dilates to a value of T ′ (see Section 5) and additionally dilates to a value of T ′′ in the case of the motion of the test particle relative to mass M (see Section 7). Due to the gravitational effect of shortening the local length, the geometric dimensions of the test particle decrease in all three spatial dimensions in proportion to the shortening of the local length. However, this decrease goes unnoticed in local observation due to the identical action of gravitation on the observer himself. Due to the gravitational effect of the allowed speed of light, the speed of light c′ in the central area remains constant relative to mass M, even if the light is emitted by a moving particle. In the case of local observation, this speed has a typical value of c (see Section 5). The same physical conditions are created in interstellar space. This means that the constant speed of light propagating from moving space objects, such as binary stars or astrophysical jets, is a consequence of the fundamental gravitational effect of the allowed speed of light, which establishes the allowed speed of light relative to the system of surrounding masses. The dilation of the proper time of various cosmic particles accelerated relative to the system of surrounding masses is also a consequence of this gravitational effect. Particles moving in different directions but at the same speed relative to the system of surrounding masses have an identical time dilation. In the frames of reference of these particles, the proper time of the surrounding stars flows faster than usual in proportion to the dilation of the proper time of the particles. Due to the fixation of the allowed speed of light relative to the system of surrounding masses, stellar aberration is observed only when the observer moves relative to this entire system. If instead, the observed star moves relative to the system of surrounding masses, then stel-Journal of High Energy Physics, Gravitation and Cosmology lar aberration is absent. Thus, the high constancy of the speed of light from astrophysical jets and binary stars, the violation of symmetry in time dilation, and the feature of observation of stellar aberration are very strong evidence of the existence of the gravitational effect of the allowed speed of light.

Gravitation and Background Radiation
The distant areas of the Universe in which the cosmic microwave background radiation observed today was formed are moving away from us at a superluminal speed. The relic electromagnetic radiation from these areas, which moves in our direction, should also move away from us, and this really took place at the very beginning. However, the fundamental gravitational effect of the allowed speed of light acts along the entire path of propagation of electromagnetic radiation. As a result, on the scale of the Universe, the speed of relict photons changes over time, but in each specific area of the Universe, photons move at the allowed speed of light c′ relative to the comoving system of surrounding masses (see Section 9) and ultimately reach us. Thus, the observation of the background radiation once again confirms the presence of the gravitational effect of the allowed speed of light.

Experimental Confirmation
The existence of the fundamental gravitational effect of shortening the local length is indirectly confirmed by four experimental facts: gravitational time delay, gravitational refraction, gravitational lensing, and finally gravitational attraction (see Sections 2 -4).
The fundamental gravitational effect of the allowed speed of light is directly and indirectly confirmed by a very large number of experimental data (see Sections 1 -10), including the constancy of the local speed of light relative to the Earth (see Section 1). Additional confirmation of this gravitational effect is the Sagnac experiment [6], which again shows the constancy of the local speed of light relative to the Earth. This is especially evident in the version of the experiment with the propagation of light around the Earth. The high-precision work of the Global Positioning System also demonstrates the constancy of the local speed of light relative to the massive Earth and the noticeable anisotropy of the speed of light in the reference frame related to the satellites. The difference in the speeds of light on these satellites along their orbit is equal to double orbital speed. As the relative speed increases, the numerical value of the anisotropy of the speed of light should increase accordingly, which is reliably confirmed by satellites GRACE and GRACE-FO (see Section 1). Thus, the gravitational experiments of the GRACE series are the key experiments confirming the existence of the gravitational effect of the allowed speed of light.

Conclusion
Against the background of many modern physical theories, general relativity is R. Sadykov Journal of High Energy Physics, Gravitation and Cosmology deservedly considered the most advanced physical theory. At the same time, special relativity is the most consistent physical theory. These theories very accurately reflect reality in all existing parallel universes, except for one atypical universe. Our Universe is such an exception. In our unique Universe, gravitation differs significantly from acceleration; in particular, the free fall of a test particle is accompanied by a decrease in the internal energy of this particle (see Section 6). This does not happen with any non-gravitational acceleration. In our amazing Universe, the constancy of the speed of light, the increase in inertial mass, and two slightly different forms of time dilation are derivative gravitational effects (see Sections 7 and 9). In our unusual Universe, gravitational attraction is a tertiary gravitational effect (see Section 4). Unfortunately, in our Universe, there is no longitudinal length contraction, but there is a vaguely similar gravitational analog that really shortens the length in all three spatial dimensions (see Sections 2 -5 and 9).

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.