Is there any other way to measure time without using any type of periodic motion. I think it's a no. A clock is essentially a periodic motion in which we measure some type of periodic displacement. I can't imagine any physical measurement that doesn't use the displacement at its core and since displacement and momentum are conjugate variables one can say that every measurement is in some form a momentum transfer. So a clock is just a reference for periodic displacement.
Is there any other way to measure time or any other physical parameter without using displacement?
The entropy is a statistical phenomenon.
Am asking it at fundamental level: Let's say in this universe there are only balls (indestructible) and reflector walls. how would someone measure time (regarding observer as omnipotent) and out of the two particle system.
And kindly give an elaborate way to measure time assuming that rate of change (is a fundamental constant) and cannot change in any way. Like burning rate of candle is not constant and can vary a lot , statistical phenomenon can't give you arbitrarily accurate time.