James R is telling you and me a load of bollocks. This from the person who insists that charge and mass are concepts. When I point out that Feynman also says "nobody knows what energy is", which contradicts "I know what energy is, it's a number", James gets all shitty. James R has repeatedly insisted he knows what A is. He knows what a distance is. For some reason, not explained, distance is not a physical object: viz. So distance must be a concept, because you can't put distance in a bottle. That is ridiculous and a completely useless argument to make. To go to the trouble of making . . . even. It's ridiculous because there is no rule in physics saying "you must be able to put physical objects in bottles". Where are the books that say anything like that? Who lectures physics students and tells them the "bottle rule"? (apart from wannabes like James?) A distance is already 'contained' anyway. It doesn't need a bottle to be in because it's 'in' the dimensions of real objects, such as planets, or humans. James' "bottle argument" falls over at the first hurdle. It's useless, it's facile. It's probably demented. James R is not, and never has been, a physics moderator. He doesn't really understand physics, apparently. Or maybe it's all an act.