Hi Eckard, Akinbo, Pentcho,
Firstly Eckard you wrote "I would not say the length of path is a matter of opinion but it is a matter of either existing or not existing reference in objective reality."
The length of an object measured at the object itself to an agreed level of accuracy is not a matter of opinion. Other observers making the same measurement with the same scale would find it the same. That is a measurement of the actualized substantial object itself. A distance between two substantial objects in close proximity to the observer can be measured from and to the objects themselves.This could be emitter and sensor or mirror. Assuming the objects in question are stationary relative to each other other observers can make and agree on the measurement.
However a distant observer can not measure the objects directly but instead measures the distance between the images of the objects produced from the sensory data received. This distance need not agree with the measurement of the object itself, or distance between objects themselves. So near and far observer can hold different opinions as to what the distance is.
Re. Your "Do we need the misleading notion observer at all if there is only one reality but many possible perspectives of consideration? "
There are two different versions of reality as I see it. One is what is, such as the unchanging length of a substantial solid object in motion. The other is what is seen, possibly length contraction of an object in motion. Though this is not seeing the object itself but the manifestation fabricated from the received data. Giving a different emergent reality that is yet still within the Foundational unobserved reality. The distant observer can not directly access the Object reality of the distant apparatus. The foundational Object reality is such that all of the different observer perspectives are produced from it and are truthful and correct from their own perspective.
It's not the observer him/her/it self that causes the difference. It is not an optical illusion generated by the brain or device but to do with how that EM has propagated, from which the emergent reality will be formed. It is about about the EM sensory data within the environment which is as real as the material objects and particles under consideration. This is actual physics, involving the electromagnetic radiation emitted or reflected or perhaps I should say scattered from the surface of substantial objects. Enabling the perspective from a given position and time that would be generated if there was an observer there. To disregard the relative perspectives and consider only the underlying physics of substantial objects and particles under direct consideration would be to throw out a great chunk of real physics. I asked Pentcho; What is the speed of light? Is it what it is measured to be or is it what it is imagined to be?
