Einstein's GR theory predicts the bending of a light path due to distortion of the space time fabric near massive bodies. Einstein and most physicists like to visualise the spacetime fabric as a rubber sheet, which stretches down with the weight of the mass, and thus will change any light beam travelling along its surface. However, this is just a graphical explanation. One should note that Einstein is assuming a gravitational field that is pulling the mass down and stretching the spacetime fabric. In his analogy, gravity is built in the geometry of spacetime. Again, GR is missing a physical model for its admittedly correct prediction. Shown above, is the same effect, which bends a light beam travelling near a massive body, explained in terms of the EMRP gravity mechanism. A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is bent around a massive object (such as a massive galaxy) between the source object and the observer.
Assume a light beam is coming from a source hidden behind our sun. When the wave approaches the massive body of the sun, a pressure imbalance will start to take place because the energy densities and hence the radiation pressures acting on the incoming photons are no longer equal. On the outside, they see an incoming flow of direct ultracosmic radiation, whilst on the side facing the sun, they see an incoming flow of attenuated ultracosmic radiation. This will result in the photons being pushed down towards the sun's surface as they travel in the direction of earth. As soon as they pass over the shadowed region, they recover the energy balance, and keep going straight again. This energy density difference perfectly explains the distortion of the space time fabric in Einstein's theory, and one must admit that in this case, Einstein's imagination was very good, considering he did not have our EMRP model (or anything else) to physically understand what was going on.
The first confirmation of a long range variation in the speed of light travelling in space came in 1964. Irwin Shapiro, it seems, was the first to make use of a previously forgotten facet of general relativity theory -- that the speed of light is reduced when it passes through a gravitational field. He had proposed an observational test to check his prediction: bounce radar beams off the surface of Venus and Mercury, and measure the round trip travel time. When the Earth, Sun, and Venus are most favorably aligned, Shapiro showed that the expected time delay, due to the presence of the Sun, of a radar signal traveling from the Earth to Venus and back, would be about 200 microseconds more than it would if the sun was not present. Later on, using the MIT Haystack radar antenna, the experiment was repeated, matching Shapiro's predicted amount of time delay. The experiments have been repeated many times since, with increasing accuracy. This experiment had for the first time shown that the constants like c and G, assumed constants in Einstein's SR theory suffered local (or regional) in the proximity of massive bodies like the sun.
So, faced with this evidence most readers must be wondering why we learn about the importance of the constancy of speed of light. Did Einstein miss this? Sometimes I find out that what's written in our textbooks is just a biased version taken from the original work, so after searching within the original text of the theory of GR by Einstein, I found this quote:"In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity ; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)." - Albert Einstein (1879-1955) - The General Theory of Relativity: Chapter 22 - A Few Inferences from the General Principle of Relativity-
Today we find that since the Special Theory of Relativity unfortunately became part of the so called mainstream science, it is considered a sacrilege to even suggest that the speed of light be anything other than a constant. This is somewhat surprising since even Einstein himself suggested in a paper "On the Influence of Gravitation on the Propagation of Light," Annalen der Physik, 35, 1911, that the speed of light might vary with the gravitational potential. Indeed, the variation of the speed of light in a vacuum or space is explicitly shown in Einstein's calculation for the angle at which light should bend upon the influence of gravity. One can find his calculation in his paper. The result is
c' = c ( 1 + V / c2) where V is the gravitational potential relative to the point where the measurement is taken . 1 + V / c2 is also known as the gravitational redshift factor.
The speed of light is not constant in a gravitational field, but depends upon the reference frame of the observer. An observer anywhere in free fall or sufficiently close to the gravitational field will conclude that the speed of light is the well known c. But, the observer far away from the source, will conclude that the speed of light decreases with proximity to the massive body. So, in general relativity, the speed of light is the same value 'c' for all observers in local inertial frames, but not the same when the observer is outside the inertial frame. This effect is one of the variants of Mach's principle, according to which inertial properties of particles depend on the gravitational action of the surrounding masses. Unfortunately, Einstein lost (actually he said he could not find it!) this concept later on in his special relativity version, which was aimed to unify gravity with the other forces, an aim which Einstein sadly admitted he couldn't succeed at with SR.
In EMRP theory, when incoming ultra cosmic energy is shadowed, it will create an energy gradient, and pressure gradient, resulting in curvature of rays as explained for the gravitational bending of light. According to Einstein, a curvature of rays can only take place when the velocity of light is not constant over its path. (In fact it will result in local variations in G as well as all other known universal constants). In a way it's very similar to a ray of light passing from air into water. One can also explain it in terms of partial conversion of energy from the photons linear KE, into rotational KE during the curved path, which reduces the linear KE (and hence their velocity) when photons (or radio waves) approach the massive body such as the sun. Remember : "The special theory of relativity cannot claim an unlimited domain of validity" , so as long as there is the presence of a shadowing effect (ie. gravitational field), we can claim such variations without contradicting Einstein's own quotation, actually with his blessing. Hence in such cases, the speed of light will vary over its path in accordance to GR. This will introduce the time delay noticed by Irwin Shapiro. This effect also sheds light on the reason for which distant galaxies seem to be receding faster than nearby galaxies. They are not! Only the speed of light is changing due to the change in amount of shadowing and the change in c and G. The same phenomenon is responsible for gravitational redshift, which normally manifests itself in the slowing down of clocks close to massive bodies.
The Sagnac setup basically consists of a rotating setup, in which the same beam of light is split in two different paths and then compared at their arrival using interferometry. In 1913, Sagnac and Boyty performed an experiment with light circulating around a rotating table. The fringe shift obtained between east and west heading directions, indicated an anisotropy of speed of light in the direction of earth's own rotation.
In 1925 an enlarged version using ring interferometry was set up by Albert Michelson and Henry Gale, in which the light took a path of a rectangle of 340 by 610 metres, that is a perimeter of 1.9km. The aim was to confirm whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The outcome of the experiment was that the angular velocity of the Earth as measured by astronomy was confirmed to within measuring accuracy. Light travelling counterclockwise around the loop was slower than that going clockwise, showing that the actual speed of light is either c-Vt or c+Vt, where Vt is the terrestrial spin velocity. Note that the ring interferometer of the Michelson-Gale experiment was not calibrated by comparison with an outside reference, which was not possible, because the setup was fixed to the Earth. From its design it could be deduced where the central interference fringe ought to be if there would be zero shift. The measured shift was 230 parts in 1000, with an accuracy of 5 parts in 1000. The predicted shift was 237 parts in 1000. The same result has since then, been reconfirmed with larger and more sophisticated equipment. In 1985, Allan et al., used geosynchronous satellites together with several ground stations to perform a planetary sized loop, in which, east travelling signals were found to lag behind west travelling ones. The famous Hafele-Keating experiment performed in 1972, aimed to support special relativity by showing that moving atomic clocks slow down, did in fact find out a less known effect: the east bound clock did in fact show a slowing down, but the west bound clock moved faster than a stationary clock in the laboratory. Unfortunately, raw data, and results which are very important for science get filtered according to what the current accepted theories expect. The same applies to Michelson-Morley experiment in 1887, in which one can still find proof of anisotropy within its raw data. In fact, Einstein himself must have recognised this later on, when in 1920, he stated 'I thought in 1905 that in physics one should not speak of the ether at all. This judgement was too radical though as we shall see with the next considerations about the general theory of relativity. It moreover remains, as before, allowed to assume a space-filling medium if one can refer to electromagnetic fields (and thus also for sure matter) as the condition thereof'. Unfortunately, his apology came too late, for the aether notion had been damaged beyond any chance of revival. He also warned us to never consider his theory as perfect, when later on in 1939, he said 'The principal attraction of the theory of relativity is that it constitutes a logical unity. If ANY SINGLE ONE of its consequences proves to be inexact, it must be abandoned'. SR specifically states that it is impossible to detect motion by measuring differences in the speed of light. The Sagnac experiment not only proves SR to be far from exact, but plain wrong. Now, you can understand the curious absence of these notable results from your scientific literature, and why these results are only barely mentioned in relation to a small 'correction' necessary to synchronise clocks in various satellites orbiting the Earth.
In EMRP, all matter in the universe is under the radiation pressure effect of the same electromagnetic wave source, and one cannot neglect any part of the universe, without expecting even the smallest change in the resultant pressure of the system in question. If one had to imagine the whole universe to be contained in a closed sphere, the EM source generating EMRP would be lighting up the surface of such a sphere from all external directions.
A fundamental issue of general relativity is that there is no fixed spacetime background, as found in Newtonian mechanics and special relativity. In GR, spacetime geometry is dynamic and is void of energy. While easy to grasp in principle, its consequences are profound and not fully explored, even at the classical level. GR is a relational theory, in which the only physically relevant information is the relationship between different events in space-time.
On the other hand, we have quantum mechanics which has depended since its inception on a fixed background (non-dynamical) structure. In the case of quantum mechanics, time is not dynamic, just as in Newtonian classical mechanics, and this raises compatibility issues with GR. In relativistic quantum field theory, just as in classical field theory, Minkowski spacetime is the fixed background of the theory. EMRP does not limit itself to the four dimensional manifold Minkowski spacetime, but is still referenced to a fixed ST background.
Over the past years, many attempts have been made to generate a gravity shield, or somehow control gravity. A gravity shield would be theoretically composed of a material which absorbs or reflects all EM radiation thus being subject to the radiation pressure of the whole EM spectrum.
A much simpler way to control gravity on an object is to modify the gravity field imbalance acting on the object. Instead of shadowing the powerful EM radiation pressing down on the earth's surface, one could generate a stronger EM radiation pressure on the lower part of the object thus providing a gravitational force difference acting in the opposite direction (upwards), thus lifting the device. This means that an object being radiated by as much large spectrum as possible of matter penetrating radiation, may eventually move in the opposite direction of this source due to the radiation pressure difference. Such method may be used to build an antigravity propelled craft, that would in theory work anywhere in space, that is, anywhere where EM fields can propagate. The higher the frequencies used, the more efficient it becomes, since for frequencies much less than Planck's the scattering mechanism will not be in the Mie regime which leads to a lot of energy being dissipated as heat, and no longer an efficient way to transfer momentum.
A unidirectional X-ray source is a moderately good candidate to achieve this. As voltages exceed 100 kV in a vacuum, the electrons will reach high relativistic speeds and gain a lot of momentum. The impact, which usually takes place on a metal target, ionises the metal atom and generates a short wavelength (X-ray) EM wave, generally in the direction parallel to the target's surface. If the target surface is cut and positioned in a way that most radiation is directed in the same direction, then radiation pressure will create a pressure imbalance resulting in motion of the X-ray source.