Dear Georgina,
The idea 4) in my comment to Eckard you've referenced is indeed very interesting. For me, it's the most interesting idea since my recognition a few years ago the Second Law pertains (and defines) 'physical time'. It can be stated in different ways. But phrasing it as in my comment to Eckard relates this idea to the CSL Postulate of SR. And in fact explains this Postulate. Along with my mathematical proof that light is a wave and not a 'particle'.
Idea 4) as stated, "all observers are at rest relative to 'empty physical space' ", is equivalent to the CSL Postulate of SR. But unlike the CSL Postulate, this idea makes sense. As it determines the meaning of 'physical space'. Just as the Second Law determines the meaning of 'physical time'. These, together, determine the meaning of 'physical Universe' in Physics. And this, of course, determines the meaning of 'physical existence'.
I used the term 'empty physical space' only for convenience. To connect this idea with what is already familiar. I don't think of this, however, as a 'container' where physical objects exist. I do not separate the 'object' from the 'space'. Whether I think of this 'internally' or 'externally'. But from our previous discussions of two years ago, you know I could just as easily have used 'ether' instead. Or better, the prime quantity 'eta' in my papers. Or perhaps Higgs field, or quantum vacuum. Though I don't know much about any of that to feel comfortable using these. But 'ether' by any other name is just as 'prime'. And as prime, it determines 'physical existence'. Whether we think of this 'within' or 'outside' us is not too consequential for me. Whichever way, one think is for certain: Nothing can 'physically exist' outside 'physical space'. And for an object to be in motion relative to this prime 'physical space' it would need to be 'apart and outside' 'physical space'. Thus, it cannot be part of our Universe!
When objects are at rest relative to one another, they are as one. When one object is in motion relative to all the others, that object is 'apart and outside' all the others. So for an object to be in motion relative to the 'ether' (empty physical space) it would have to be 'apart and outside' the 'ether'. Thus, such object would not be existing in our physical Universe. No object can physically exist in motion relative to the 'ether'. Equivalently, all physically existing objects are at rest relative to the 'ether'.
Thanks for the opportunity to explain my thoughts to you.
Warm regards,
Constantinos
