Originally Posted By: socratus
So, in my opinion the essence of Einstein’s SRT is question:
What will be happen if the particle – quantum of light – changes
its constant and straight movement in the vacuum.

That question is answered by General Relativity (GR), not Special Relativity (SR). SR is special because it only addresses constant motion. Your question of changes in motion are examples of accelerated motion. Einstein knew this and spent the next 10 years, after publishing SR, in coming up with GR. GR takes into account accelerated motion, which he realized is the same as gravitation.

One thing, you keep talking about a quantum of light. Both SR and GR apply to any form of matter, not just light.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.