Tom, John M,
I wrote:"Elapsed time ... is an absolute measure."
Tom objected: "If it were, it would have have an absolute point of reference, contradicting your previous statement."
It has indeed a natural point of reference: the actual now. I don't see a contradiction to my previous statement: "Genuine relativity means lack of a preferred point of reference. 3D space lacks such point. Elapsed time doesn't."
John pointed to Barbour who referred to Newton. While Barbour's apparent denial of time might be seen as an attempt to defend the block universe, Newton's reasoning seems to be worth a scrutiny. Newton distinguished between
- absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration and
- relative, apparent, and common time, is some sensible (= observable) and external measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.
My distinction between absolute and relative refers to the criterion whether or not there is a natural point of reference. In this sense, Newton's relative time is my absolute one and vice versa,
I resonate with Barbour's utterance: "I shall show that intervals of time do not pre-exist but are created by what the universe does." Indeed, while the future is thought to pre-exist as something unknown in principle, it wouldn't be reasonable to confuse expectations with reality.
Tom added his credo: "Only spacetime -- not time alone nor space alone -- is physically real." I see spacetime rather a questionable construct that was never measured so far but hinders people to believe that my spectrograms are correct.
Eckard
