Is the speed of light constant? (2)

I told some people about my assumption that the speed of light is not constant, and one of them agreed that it might not always be constant for quantum particles, but the average speed of light in empty space is constant. But my question is – what is empty space? Can complete empty space really exist? Does quantum mechanics allow it? And if not – do all areas of space have the same level of emptiness? Do they all have the same average level of emptiness? Does the level of emptiness remain constant in time?

It appears to me that the level of emptiness (and the average level of emptiness) of space cannot be constant for all spaces in all times. Einstein’s relativity says that if one travels close to the speed of light, space shrinks in one direction. Since I assume complete empty space is not possible, at least not on the macroscopic level, at least not in this part of the world, then it appears to me that when space shrinks, the level of emptiness changes too, and the speed of light will not be the same as before?

What happens when one travels very close to the speed of light? Is it really possible to travel 20 million light years in less than one second? If someone travels that fast, how will it affect the speed of light? Space will definitely shrink, become more condensed, and we know that the speed of light in water is slower. Will he see the speed of light as a different speed in different directions? Will the speed of light in his direction become slower for him? And how will this affect Einstein’s formulas, such as E = mc2? Will they be affected too?

And what happens when galaxies drift away from each other? Is more space created between them? Is it emptier than before, or are new quantum particles created too? It appears to me that our perception of space and time are created by our definition of entropy, which is the level of uncertainty of what we know and don’t know. Is the average speed of light constant by definition, or can it be affected too? Can one be at more than one places in space at the same time? Can simultaneous events happen? Is it possible to change the past, go back and choose another future? I really don’t know.

Michelson and Morley didn’t check this. The speed of Earth is much lower than the speed of light as we perceive it, space seems to have the same level of emptiness in any direction. The speed of light, as they perceived it, was almost constant. Einstein concluded there is no aether. But Einstein believed in determinism. He didn’t like to think about God playing dice. Since determinism leads to a contradiction, Einstein’s relativity is not fully consistent. His conclusion may appear to contradict itself. Aether may appear to exist.