Eckard
I will have to be careful here, as it may not be what you are saying. But there is no duration in physical existence. Hence even the application of x = vt can be flawed (and indeed is). So by definition, there is nothing to be symmetrical about.
Either one stays within any given time and compares different physically existent states at that time, or one compares sequences of these as they progress over time. The point about x = vt is that distance, which is a difference, can only occur between two physically existent states which are existent at the same time. So any given distance is always unique, since it reflects a definitive physically existent circumstance at a given time. Notions which relate to the quantification of it in terms of space, or duration, and the comparison of one way with the other, are a fallacy, if they involve the presumption that there could be a difference. Whatever quantification methodology, there can only be one result.
The exception to this is that distance could be conceived as a single example of change, ie a difference. So it can be expressed, conceptually, in terms of duration incurred. The concept being that instead of expressing distance as the fixed spatial quantity which it is, it can alternatively be quantified as the duration which would have been incurred had any given entity been able to travel along it, either way. But it must be understood that there is no duration as such, this is just an alternative to, and the equivalent of, a spatial measure, ie a singular quantity. Failure to understand the absence of elapsed time in a physical reality results in the flawed application of the equation x = vt. Making this mistake reifies change, and hence duration.
Now look at Einstein1905, it falls over from the start. Even worse, distance is seen as being quantifiable in terms of subsequent timings, not just it is a duration.
Light is 'constant' in that it is an existent phenomenon. It is not dependent of being received (ie observation). It results from an atomic interaction, so it always starts at the same speed, ie the speed of what it reacted with is irrelevant, because it is not a collision. There is no dichotomy between 'constant' light speed and a variable timing. It is just that the latter is in the receipt timing of light, not physical existence. All other things being equal, then the time of receipt of light which carries a representation of any given existence will be a direct function of distance between observers and existence.
Light as in waves, etc, ie over time, is another issue. Here we need to understand how light works. How many photons are involved in a 'decipherable' light, does exactly the same effect in photons disperse in all directions after an interaction, what is the differential between one light and the next, how does the effect actually travel, ie does the effect itself move, or is it a chain reaction, etc etc.
Be careful with SR, it is not 1905. SR is a theoretical circumstance without gravity. So it involves fixed shape bodies (ie no dimension alteration), only uniform rectilinear and non-rotary movement, and light that travels at a constant speed in straight lines. It was his way of demonstrating that there was no inherent contradiction in the two postulates. Note the phrase "only apparently irreconcilable" when stating them in 1905. Now that is weird, a new theory, only requires two postulates, and yet the author is aware that those who have brains might spot there is an inherent contradiction somewhere. But the author does not explain why it isn't at that time. Just 'resolves' it later with a purely theoretical circumstance, then moves on to the actual theory, ie GR.
The point about 'frames' is this: it is a reference. The reference for both time and space are concepts. They have to be operationalised. So any given timing device or spatial measuring device is just 'telling' the quantity. It is, in practical terms, the best approximation we have to the concept, which enables us to compare differences. Those watches of Einstein's were in synch already, otherwise they are useless. There was no "common time" to find.
Having been stimulated by an exchange with Ben, I have written the core argument down. I am now wading through all the other stuff. I do not have the capability to be specific, but my view is becoming that this search for a stationary reference and consideration of ether/light/etc was a red herring. There is no problem. Obviously light arriving at earth is affected by a number of factors, but light here on earth? The immediate reaction, ie dimension alteration, just sort of gets left on the cutting room floor. Timing is the new kid on the block, thanks to the flawed concept of simultaneity. One gets 'echoes' of dimension alteration in the idea that it is OK for clocks to differ when they move, because movement is making them contract/elongate so they tick more slowly/faster.
Paul
