Clarification:
I feel to clarify my short remark of my last message. Definitions
are (by definition) arbitrary (as long as they are meaningful). In that
sense, they are needed to know what we are talking about, they are
SEMANTICS, not physics. As such, I have little interest in them.
But what I find interesting is the discussion of problems associated
with possible definitions of a concept, apparent (or real) contradictions,
limitations, etc. etc. That is real PHYSICS. Best regards, Emilio