I would like to know, does anyone know of specific examples of quantum measurement of energy? The reason I am asking is that anything that is observed is ultimately in a position space as opposed to momentum space (for example, it might be specific position of the errow of a measurement device). So, does energy measurement ultimately involve position measurement? If so, how can we get around the uncertainty relations? I also have a related question: how is it possible to measure an energy of a single particleanyway? For one thing, its energy is very small, so how can it be suffi cient to cause something classically observed. Also, in light of second quantization, a particle can decay any time.