Pasti: ''As for the example you gave regarding mass and energy, personally I am more inclined to agree with the one saying that in fact they are not the same (I guess this would be the physics professor). Mass is still a measure of inertia (you cannot disregard the marticles with rest mass), while energy is significant in conservation laws. Sure, there is a definite relation between them, but they are principially not the same, in my oppinion. They describe different concepts, in spite of the traditional “equivalence between mass and energy.''


Well, this reminds me of heat and energy:


http://sci.tech-archive.net/Archive/sci.physics.research/2004-08/0314.html