The Galilean principle is mentioned in passing. That an object within a carriage sealed from visual contact with the outside will be seen by an observer in that carriage to move as it should. Thus it is indistinguishable Whether the object is in a moving carriage or not.
The movement of the carriage is conveyed to the object and to the air within the carriage! We must take this further. Whatever is within that carriage is moved in concert with the carriage, thus whatever medium or aether or property by which some physical power exhibits itself is also moved.mthus we say the laws of physics hold in any uniformly moving frame of reference. By this we mean that that motion of the frame is imparted to any phenomenon within that frame.
How then do some say and teach that the speed of light is a universal constant? That nothing travels faster than the speed of light? It is clear, by the Galilean principle that light or any object travels at its speed plus the speed of the frame in which it is emitted!
The question is can we observe anything moving faster than light? Clearly not, but what we can observe are the Doppler shift effects due to portions of a light beam ( or a sound wave) crowding in to tHe medium of transmission!
What if the medium of transmission moves independently of the carriage? Then we would expect some Doppler like variations in the light signal. At sea level Michelson and Moreley found no variation. However at higher altitudes scientists have found perceptible variations! At those heights and densities the relative motion of all mediums is not sufficiently coupled to the earth to fulfill Galileos principle.
The speed of light is not an immutable constant, but it is limited as a bulk property of any medium. Thus Lorentz contractions or Doppler shift effects do have to be accounted for in measurements using light or radiation, not because nothing can travel faster than the speed of light but because we cannot observe anything travelling faster than light speed.
Suppose now we make a measurement and by calculation it comes out faster than light speed, the question is how have we “observed” that? If we have not accounted for light speed limits in a material correctly we will make an error. For example if I measure light through different media I get different speeds . How is that constant? The assumption of a constant or maximum speed comes from a bulk property analysis. It is assumed to be maximum in a vacuum. However what if it is a maximum not in a vacuum but in some other material? How will we know?
Finally what if some other phenomena is actually faster than light, but can be detected by instruments that do not rely on light or electromagnetic radiation? Neutrinos are posited as neutral electromagnetically. If they travel faster than light and we use a statistical average detection method rather than direct observation we may very well ” detect” faster than light statistical averages!
Some investigation is in order rather than dogmatism.