I'm not sure if it makes sense to explain physics in English because it tends to get really imprecise and unclear. That being said, suppose you have a theory w

I'm not sure if it makes sense to explain physics in English because it tends to get really imprecise and unclear. That being said, suppose you have a theory which describes physical processes. Given that this theory must hold true for every variation of some parameters (rotation, translation, time, ...) then you can derive some things which are constant (angular momentum, linear momentum, energy, ...). Now one can spend many hours thinking about the relation between energy and time with fuzzy philosophical definitions or one can just accept that the math turns out that way (given some assumptions of that theory).