> They have chosen their particular physical process: "as if someone stood with a stopwatch" It's not well-enough defined for all purposes. Where is that pers

> They have chosen their particular physical process: "as if someone stood with a stopwatch" It's not well-enough defined for all purposes. Where is that person standing? Earth's surface is shifting and moving all over the place willy-nilly, so how do you define that particular location in the first place? Over what timescales is that definition valid? What physical process do you mean by stopwatch? What particular synchronization protocols do you define? What physical models do your definitions invoke? Answers to these kind of questions will generally generate mutually-disagreeing time standards. I mean, with suitable transformation rules, they'll often agree up to some precision limit, but if you need anything beyond that, you've now gotta choose the one(s) that best correlate with the natural ticks in your problem domain. Also, any standard like "someone standing with a stopwatch" is forced to just a fiat declare the stopwatch as the Definition of Time, a la the platinum sphere kilogram. We all know how great that was. Do you now want a team of canonical stopwatches and some aggregation process? How do you deal with measurable drift between the tick rates?