> If you can't distinguish kinetic from potential in this circumstance, does the definition of 'kinetic' and 'potential' have any rigorous meaning? They're sti

> If you can't distinguish kinetic from potential in this circumstance, does the definition of 'kinetic' and 'potential' have any rigorous meaning? They're still different forms of energy even if you can't see which is which from the outside of a (non-transparent) box. Like, if you have a red ball in one and a blue ball in the other, you can't see from the outside which colour ball is in which box either. Does that mean "the concept of colours doesn't have any rigorous meaning"? No, it just means the concept of being in a non-transparent box has the rigorous meaning that you can't see what's going on inside it.