DT,
This is a challenging writing topic, but I'll give it a try. Not my specialty, but I have had exposure as well...
When I first scanned your introduction, my knee jerk reaction was to respond and somehow say something in support of relativity theory being a theoretical answer to physical observation. But then when I look more closely at what you said, I don't think that would be necessary. It sounds like you've been examining the subject for yourself and find it plausible enough to defend in argument yourself.
To others I would say that special relativity arrived on the scene because there was an odd discrepancy in physical observations: No matter what motion was observed in a source of light, arriving light seem to be moving at the same speed. And if the speed always remained the same, then maybe time was not absolute... The physical and geometrical implications are included in college introductory physics courses, but the philosophical implications are left to the student. Special relativity was the camel's nose of this initial observation. General relativity gave us a concept of space and time that made time another dimension which was warped by mass - or as the saying goes:"Space time tells matter how to move, matter tells space-time how to curve." In the space of 10 years from 1905 to 1915 Einstein and some correspondents worked out most of the deep implications of this theory, derived from the initial observations...
And continually confirmed by subsequent experimental observations ( residual movements in celestial space of Mercury's perihelion, the bending of light in neighborhood of stars about twice what Newtonian theory would predict...) and practical applications (GPS satellite programming includes corrections for relativistic effects).
Speaking of Newton's theory, celestial mechanics for centuries and present day space navigation have done very well without Einstein, save for:
- such small discrepancies in the solar system
- and much larger effects elsewhere in the universe where there are objects where motions often approach light speeds
- or in the laboratory with particle accelerators
All these regions depart from newtonian mechanics. But what's more. Newton never had an explanation for why matter attracted other matter. Einstein's GR does. Matter warps the shape of space. And energy has an equivalence to matter ( e= mc^2) - so that means a sphere of energy would alter the path of passing matter as well - just by being intensely "hot".
And in describing the physical world - all this seems to work.
That's about where special and general relativity theory stand. Explanation. But as edifices of human thought, they are as excellent as anything ever produced.
Is there no argument about either in the science community?
I wouldn't say that. There have been periods of neglect between 1915 and the current day, because GR seemed to be removed from practical application other than an explanation for stellar evolution or making bombs. But there have been controversies within it.
In recent years my e-mail box has been stuffed with arguments about the nature of GR and the discussions have been heated. One that is easier to characterize than most is the issue of inertia and Mach's contribution to Einstein's thought. Since Einstein explained attraction of bodies there was still the question of where does inertia or centrifugal force come from? If a bar bell with two masses were rotated in space, an inhabitant on one of the ( balanced ) pair would feel accelerations. He might become dizzy as he watched the spin of the fixed stars. Mach attributes this effect to the fixed stars, the entire mass of the universe causing a resistance....
OK. Now what if there weren't any? You wouldn't be able to tell if you were spinning or not. What if there were fewer or farther away? Would the acceleration be less. There are arguments pro or con or whether the effect is attributable to the total mass ( and energy) at all. But would either answer overthrow GR? Hardly.
Researching this question I found that Mach was a proponent of positivism. Which is to say that he did not believe in atomistic theory since there was no "observational" evidence for them in the 19th century. So he advised Einstein accordingly. Einstein at first adhered to his general advice, but broke with him later. On the other hand, Thompson in England attributed experimental results to a particle he named the "electron". Kaufman in Germany with better instruments and procedures saw the same phenomena more clearly, but discovered nothing. He was a positivist.
I gotta go...