Reference: Disturbance Theory
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“The situation grows more and more serious. Two assumptions have been tried. The first, that moving bodies carry ether along. The fact that the velocity of light does not depend on the motion of the source contradicts this assumption. The second, that there exists one distinguished coordinate system and that moving bodies do not carry the ether but travel through an ever calm ethersea. If this is so, then the Galilean relativity principle is not valid and the speed of light cannot be the same in every coordinate system. Again we are in contradiction with experiment.”
~ Albert Einstein, Evolution of Physics by Einstein
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The null results from MichelsonMorley’s experiment in 1887 initiated a line of research that eventually led to Einstein’s theory of Special Relativity. The expected difference between the speed of light in the direction of movement through the presumed aether, and the speed at right angles, was found not to exist. The special relativity then ruled out a stationary aether.
Light seems to have both wave and particle characteristics. As a wave, light requires a medium; and as particles, light requires some system of coordination among particles. In either case, light requires some relationship within its background, which is space, even when there is no aether.
There seems to be an assumption that moving bodies travel through space without resistance. We do not see space. We can only see a body moving relative to another body. How do we know that a body is moving relative to space?
We all know about inertia. Newton defined it as follows:
“The vis insita, or innate force of matter, is a power of resisting by which every body, as much as in it lies, endeavours to preserve its present state, whether it be of rest or of moving uniformly forward in a straight line.”
If we postulate that inertia is the resistance of space to a moving body then a lot of observations fall into place.

When there is acceleration then we know that a body is definitely moving relative to space.

When there is no acceleration then a body’s acceleration is balanced by inertia.

Light has a finite and constant speed because its acceleration is balanced by inertia.

A body has a constant drift speed in space when its acceleration is balanced by its inertia.

The drift speed of any object shall depend on its inertia.
We may then postulate space to be the background of no inertia in which bodies with inertia are drifting at speeds that depend on their inertia.
The difference between the speeds of light and the earth shall be constant because the difference between their inertia is constant. This explains the null result of MichelsonMorley’s experiment.
One may object to the above by saying, “The earth is orbiting the sun. Therefore, it is constantly accelerating in the radial direction towards the sun, but not in the tangential direction. So, there must be a slight difference in speed relative to light in the two directions.”
We may calculate the order of this difference as follows:

The difference between the disturbance levels of the earth and light is roughly 186 (235 – 49). Therefore, the ratio of their frequencies is 2^{186}.

The ratio of their drift speed shall then be 2^{93} or 10^{28}.

The drift speed of the earth shall then be (3 x 10^{8} meters/sec) (10^{28}) = 3 x 10^{20} m/s.

The MichelsonMorley’s experiment is then required to detect a velocity difference of 6 x 10^{20} m/s.
So far there has been no MichelsonMorley or another type of experiment that has the level of accuracy to detect the speed of the earth relative to “aether”, which, in this case, is space.
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Conclusion
Thus, the null result from MichelsonMorley’s experiment is questionable when we consider space to be that elusive aether.
This then also makes the postulates of special relativity questionable when we consider inertia to be the resistance of space to a moving body.
This then limits the validity of the theory of special relativity to the explanation of phenomena where speeds involved are much smaller compared to the speed of light.
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Comment (1/5/2019):
Moving bodies do not carry aether along because there is no aether. There cannot be stationary aether because only a system of infinite inertia can be stationary.
There is only a very ephemeral form of substance with inertia less than that of light. Light has its own inertia, which determines its velocity. Similarly, the source of light also has inertia that determines its velocity. Each velocity is constant in the coordinate system based on a scale of inertia.
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Comments
Uniform velocity in space is indistinguishable form “rest”. That means that an object moving uniformly in space is at rest relative to aether. It is moving relative to another object in space and not relative to aether. So the object will move relative to aether only when it is accelerating.
MichelsonMorley’s null result is questionable in my opinion. Speed of light is a universal constant only in the ‘Space Reference Frame’ and not in the inertial frames of moving matter.
The theory of Relativity assumes that the speed of light is a universal constant in the inertial frames of moving matter; and explains this null result by contraction of space and dilation of time with increase in velocity.
The Disturbance theory points out that velocity increases naturally along with contraction of space (increase in wavelength) and dilation of time (increase in period) as one moves down the electromagnetic spectrum.
The aetherdrag theories are considered to be disproven. Special relativity completely disregards the presence of aether. But if we consider INERTIA in place of “aether drag”, we find that Special relativity fails to account for it. The Disturbance theory nicely accounts for inertia as the “resistance to motion put up by space”.
Space Reference frame (SRF) is the frame of ZERO INERTIA.