With the Michelson Morley experiment, scientists were certain they had reached the clearest verification of the fact that the aether was an outdated, non–scientific concept.
But the Sagnac’s experiment is the evidence that the aether does exist. How to explain the Sagnac effect? It is a physical phenomenon of interference discovered by the French physician Georges Sagnac in 1913. It is an asymmetry of the relative speed of two light beams
that run in opposite directions the circumference of a rotating disc.
In this experiment, an annular interferometer was used. The figure above is the schematic image of the interferometer used by Sagnac to split a light beam into two different beams running the platform in two opposite directions. When the two opposite rays arrive again to the starting point they give an interference pattern.
But we can try to reason on a somewhat simplified version. Let’s suppose that the platform rotates counterclockwise as in the picture. The blue beam propagates in the same verse of the rotation of the platform. The red beam moves in the opposite direction. ω is the angular speed of the rotating platform. R is the radius of the platform coincident with the
circumference run by the two light beams.
While the two rays move, the platform rotates. As a consequence, the two rays match and interfere in a point different from the starting one. They will encounter in a point moved in a counterclockwise direction, like the rotating verse. The two rays are running thus different distances in different times. The blue ray will run an entire circumference plus a
fraction of a circle. This blue ray will take thus a time:
where ωR is the linear speed of the platform on the edge, where the light moves. In the figure below you can see an image of the interferometer. Similarly, the red ray will run less than a circumference and will take a time:
We can thus obtain:
The two rays have thus a total amount of delay:
since ωR<<c. Since the Area of the circle is A=πr2 we obtain:
and the phase delay will be:
We can notice that, once we have fixed the geometry of the platform (area A), and the type of radiation (wavelength λ), the fringe displacement will only depend on the angular speed of the platform ω.
The two light beams move at the same speed: the speed of light. A ray will run a minor distance because the platform rotates toward it. This is in total disagreement with the special relativity statements. Let’s imagine an observer on a fixed reference system not rotating with the platform. In that case, which will be the resulting speed due to the movement of the
platform? The light beam moving in the opposite verse of rotation of the platform will have a speed given by the speed of light added to the speed of platform. The amount will be more than the speed of light and this is against Einstein’s assertions.
This proves that light follows the normal Galilean relativity. We can say, as a conclusion, it is not scientifically correct to state the speed of light is always the same, regardless of the reference system. This is a surprising deduction and shows that the Michelson Morley experiment should be interpreted another way. Since this discovery was made after Einstein had introduced his theory of the special relativity, no one was bold enough to say a word.
There is no measurable aether wind on Earth because the Earth is motionless.