"Special Relativity": The strongest direct evidence comes probably from particle accelerators, in which subatomic particles such as
electrons and
positrons are accelerated to within a few inches per second of the
speed of light. We can observe very clearly and accurately the changes in, for instance, the apparent masses of the particles. They are observed to increase dramatically, and in fact new and much heavier particles can be created by making counter-rotating beams of, say, electrons and positrons, collide head-on with each other.
Special relativity has played a key role in the design and operation of particle accelerators for many decades.
Hi Felix; The above is from the Goddard Space Flight Center. While both the big bang and SR are theories there is pretty good evidence for both. SR also had the experiment where clocks ran different, when accelerated, as predicted by the theory. But, needless to say, you are entitled to your own theories. Best to you Felix, Pat