False claims

The dogma is that the speed of light travels at a maximum velocity of 186.000 miles per second in vacuo, or only in a vacuum.  No vacuum exists anywhere in the universe, so this postulate is false.  In reality light travels at different speeds depending on the medium and this upends Relativity and most of modern science.  Since we cannot measure anything in a vacuum the claim that there is an upper end to the speed of light is mere speculation.  It might be correct, but it could also be completely erroneous and could well vary over time.

It needs to be stated that light is independent of its source and therefore light waves require no medium for their propagation.  Light emission is premised on electrons and electrical energy.  Light is basically a wave in an electromagnetic field (Faraday, Maxwell), and when this is propagated through a medium (air, water, an object), its speed will vary in accordance with the properties of that medium.  

We also know that all wave speeds, like object speeds, must be measured relative to some object on which points A and B can be specified or mapped out.  This is called a frame of reference (or a grid map).  We can only measure light speed relative to an object on a grid (hence points A and B representing starting and ending points or 2 objects relative to each other). 

Logically we cannot measure the speed of light in a vacuum since reference frames and objects don’t exist in vacuo.  The speed of light in a vacuum is thereby a theory devoid of meaning.  It should also be noted that many scientists don’t believe that the speed of light can even be measured.

“But several physicists have pointed out that while relativity assumes the vacuum speed of light is a universal constant, it also shows the speed can never be measured. Specifically, relativity forbids you from measuring the time it takes light to travel from point A to point B. To measure the speed of light in one direction, you'd need a synchronized stopwatch at each end, but relative motion affects the rate of your clocks relative to the speed of light.” (Koberlein, 2021)

More on this quote below.

We should also emphasise that measuring speed and time is entirely a human invention.  It is our conceptions of motion and time which allow calculations of velocity and duration.  Time does not exist outside of human consciousness. Therefore time can never be merged with space into a new spatial-duration dimension.  More here