quote:I just think a lot of confusion arises when a laymen (like myself and Heinrik) tries to understand the equation if that's not explicitly stated.
Well, I don't think this is the source of the confusion, actually. I think the source of confusion is that laymen put too much values in the words while real physicists only use words as tools to communicate with other people.
The words "energy" and "mass" are just linguistic representations of what physicists observe. Tomorrow, we could call it "hoogabooga" and it still wouldn't change what it is.
I think the best way for laymen to understand these concepts is that they try to not put too much value on semantics and more on the concepts and mathematics of it.
But yes, "mass" can be understood as just a form of "energy".