Michelson-Morley experiment (MMX) was devised on the premise that as Earth moved through the stationary Ether medium, it would result in what is called as the Ether wind. And it was proposed that light beams passed in different directions i.e. one beam passed perpendicular to the direction of the Ether wind and another passed along the direction of the Ether wind would take different times to travel the same distance. Michelson apparently used swimmers analogy to illustrate the logic behind this proposition – When two swimmers with equal competence are asked to swim to and fro for equal distance in a flowing river, the swimmer who swims straight across the river apparently will take a shorter time for the round trip than the one who swims first down the stream and then against the stream. So it was predicted that the light beam which travels perpendicular to the Ether wind would take shorter time than the beam which travels down the Ether wind in the first half and then against the wind in the second half of its journey. So scientists predicted that the two returning beams would be out of phase when they meet finally and hence would result in interference on the detector screen. Further they thought that the time delay and hence the degree of interference would vary depending upon the orientation of the interferometer arms with respect to the direction of the Ether wind.
But to the astonishment of the scientific minds, the experiment yielded no interference between the returning beams. It implied that both the returning beams have arrived at the half silvered mirror at the same time contrary to their expectation that the ‘perpendicular beam’ would take longer for the return trip than the ‘parallel beam’.
To the scientists, the null result i.e. the lack interference between the two beams implied two possibilities. Either there wasn’t anything called Ether or Earth must be dragging a blob of Ether around it in which case there wouldn’t be any Ether wind to detect. Apparently evidence from other observations (aberration of star light, Fizeau exp, Sagnac effect etc) had disproved the possibility of Ether drag, and so the scientific community was forced to interpret the null result in MM experiment as disproof of existence of Ether medium.
To understand why MMX is based upon a wrong premise and hence incapable of drawing any valid conclusions about Ether, first we will have to answer two important questions.
1) What is actually the basis of the so called Ether wind?
2) Can Ether wind exist without Ether being dragged?
We all know that, even when the climate is quiet and the air is motionless, we experience air winds if we go on a bike ride. Similarly a ball moving inside a pond of still water also experiences what may be called as water wind. But how do we explain this phenomenon of wind? In other words what is the physical basis of this experience of wind? Irrespective of who moves and who is still, it is obviously collisions that our body receives from the air particles which makes us experience the so called air wind. And same is the case with the ball. As the ball moves through the still water, it receives collisions from the water particles and it is these collisions which make the ball feel the ‘water wind’.
And what happens to the water particles? As the ball hits the water particles, they obviously move in the direction of the force. In other words the particles get dragged by the ball. And the ball drags not only the particles which come in direct contact with it but also the farther away particles by way of indirect collisions.
In summary, whenever a body moves through a stationary fluid medium, the body drags the surrounding fluid particles with it. And the scenario of a body (Earth) experiencing a fluid wind (Ether wind) but not drag the fluid doesn’t simply exist. And so is the scenario of a body dragging the fluid medium but not experience the fluid wind. The wind effect and the drag effect are inseparable and result from the same fundamental mechanism i.e collisions between the body and the medium’s particles. It may be true to say that while it is the moving body which experiences the wind effect; the medium’s particles experience the drag effect.
So if someone blames Ether drag for his experiment’s failure to detect Ether wind, that only exposes one’s poor logic because the experimenter must have already realised and incorporated the drag effect while devising the experiment to detect the Ether wind. And if someone looks for Ether drag to explain the lack of Ether winds, that obviously shows one’s lack understanding about both Ether drag and Ether wind.
If someone without any idea of how and why Ether drag occurs and who is wrongly convinced that there are no Ether winds claims to disprove the phenomenon of Ether drag, we can imagine how much reliance we can place on those claims.
As explained elsewhere, double slit experiment and the phenomenon of gravity provide clear proofs for the existence of photon Ether and differential Ether drag respectively.
Basically MMX is incapable of detecting the Ether wind. If it were, we could devise a similar experiment with sound waves and water waves to detect air winds and water winds. The reason is the motion of a source affects the velocity and direction of propagation of the waves that it generates. For example imagine a stationary oscillator generating water waves which propagate towards East. Now imagine the oscillator moving in the northward direction. The water waves that it generates now propagate mainly in the north-east direction instead of in the eastward direction. We all know that this is what happens in our everyday life with projectiles or particles. As I have discussed elsewhere, at the most fundamental level, what underlies wave motion is nothing but to and fro motion of particles and the various phenomena of wave motion (e.g. interference) can be explained purely by particle model. So why should we expect waves to behave differently from particles?