| I sometimes wonder, what is real and what is a concept in physics: is that force , energy, ...? There are often two ways to solve physics problems: one describing the problem with forces, the other reasoning with energy. So they look like the two faces of the same coin. Hence the question: which one is actually real? Some quick arguments for and against Energy: + converts between mechanical, chemical, thermal, radiative types, and even mass + quantum particles, when interacting, exchange energy - looks like an integrative quantity (in the sense of mathematical integral) Force: + feels very real, when you receive a ball in your face + we talk of fundamental forces, not fundamental energy + explains momentum, deformation well - my physics teacher used to say "nobody ever saw a force" - force is undistinguishable with acceleration - at the quantum level forces are actually particles interacting - at the quantum level, the uncertainty principle makes the newtonian force pointless (pun?): seems like we could know the vector's origin or the direction but not both |