UNILATERAL MEASUREMENT OF LIGHT SPEED
Measurements on light from double stars were used to show that the one-way speed of light is independent of the velocity of the light source.
The one-way speed of light relative to a moving observer is determined using the range measurement equation of the Global Positioning System. This equation has been rigorously tested and verified in the Earth-Centred Inertial frame where light signals propagate in straight lines at constant speed c. The result is a simple demonstration of light speed anisotropy that is consistent with light speed anisotropy detected in other experiments and inconsistent with the principle of light speed constancy. This light speed anisotropy was not observed before because there has been no direct one-way measurement of light speed relative to a moving observer.
The one-way speed of light is determined using the range equations employed in the tracking of planets and spacecrafts moving within our solar system. These equations are based on the observation that light travels in the sun-centered inertial frame at a constant speed c and have been extensively tested and rigorously verified. For light reflected from an object moving in space the light speed detected on the surface of the moving Earth is found to be c+v and c-v relative to the receiving antenna for the Earth moving at orbital speed v in directions toward and away from the reflector. This finding is consistent with results first presented by Wallace and later by Tolchel'nikova but is at variance with the postulate of light speed constancy.
In order to confirm this preferred frame detection, the GPS clocks were utilized in a modified Michelson-Morley experiment where the clocks replaced the interferometer. The clocks measured light travel times along the arms of the apparatus and revealed ether drift arising from the Earth’s rotation. This direct determination of the light travel times rendered the measurement essentially immune to the second-order length contraction phenomenon which negates the fringe shift in the conventional Michelson-Morley experiments. The GPS technique did not require actual time measurement but utilized light travel time that is directly available from the CCIR clock synchronization algorithm. The modified experiment succeeded in detecting ether drift for rotational motion while the majority of other Michelson-Morley-type experiments are considered to have produced null results. In the approximately inertial frame of the experiment, special relativity is directly applicable and predicts a zero time-of-flight difference between equal orthogonal arms and hence a null result.
Contrary to this prediction of special relativity, the modified Michelson-Morley experiment detects non-zero time-of-flight differences corresponding to ether drift and thereby reveals a preferred frame as previously reported by Gift and Shtyrkov and also by Demjanov and Galaev.
The results of the positive test for a fringe shift in the Cialdea experimental setup has shown that the device is actually incapable of showing a relative phase shift between the two beat signals, even when one should be present due to a deliberate change in the speed of light in the path using glass. The only conclusion that we can take from this is that the experiment of 1972 actually proved nothing - it is not a verification of special relativity, nor does it disprove any ether theory. The Cialdea experiment was first criticised by Tyapkin , who argued that the change in phase due to the change in time along the independent path between the lasers when the device is rotated would be exactly cancelled by a change in phase of the light in the laser output. Mansouri and Sexl  also commented on the Cialdea experiment, suggesting that Tyapkin's theoretical dismissal of Cialdea's first order experiment was incorrect. However, neither of these authors actually attempted to replicate the experiment. The problem appears to be simpler - the beat signals displayed on the oscilloscope are shifting phase already at high speed due to the frequency differences between the independent lasers. Any possible phase shift that might occur between the two beats due to an ether wind would occur over a timeframe of several seconds as the device is rotated, and if it did occur, it would immediately be lost in the rapid phase shifts of the beats, that are changing on the order of 100's of millions of times per second. The time base (sweep triggering ) of the oscilloscope cancels or obscures all of the relative phase differences that might arise due to rotation. Although Cialdea points this out, he suggests that overlapping more laser frequencies will eliminate this problem. Clearly it does not, since in practice no phase shift can be made to occur even with our positive controls. This highlights the problem with relativity experiments that attempt to prove a point with a negative result only - without at least a good positive control, how can we know that the experiment even works?
In the original premise of this experiment in was believed that this interferometer would be successful in detecting an aether drift if a preferred medium of space exists. However, , as has been explained in the discussion, this anticipated result turns into a null result when one takes into account the frequency shift of the laser clock due to its rotational motion around the table. This frequency shift is called for in both Lorentz ether theory and relativity, and thus within the resolving power of this experiment we cannot distinguish between the predicted result of the two theories. This same frequency shift in the rotating clock is the reason why other one-way speed of light experiments with rotating lasers, masers, or using the Mossbauer effect cannot distinguish between the two theories.
Described herein is a replication of Silvertooth’s experiment of 1986/1992. The analysis starts by re-performing the wavelength difference method described in these two papers and examining the distance required to move a standing wave sensor (SWD)/mirror system on a translation stage to register a phase inversion. After performing this procedure repeatedly over a number of sessions between June and December 2011, a similar 12 hour pattern of change was seen conforming to the original observation of Silvertooth. The experiment is then repeated using a new method involving measuring the frequency generated at the two sensors using an oscillating stage driven by piezo actuation. Finally, experiments are performed to try to determine the true cause of the diurnal pattern of presumptive wavelength change, focusing on the HeNe laser and its beam pointing stability over time. The final conclusion is that the wavelength of light measured in the system is not changing in a manner dependent on sidereal direction. The cause of this diurnal pattern turns out to be something far more mundane.