To my mind, questions like „How exactly do protons, neutrons, electrons or atoms etc. exist?“ cannot be answered. Here, I am following Paul Davies who puts it in the following way (in his introduction to Werner Heisenberg’s “Physics and Philosophy”, Penguin Books):
“By contrast, the Copenhagen interpretation of quantum mechanics, which Heisenberg here expounds so lucidly, rejects the objective reality of the quantum microworld. It denies that, say, an electron has a well-defined position and a well-defined momentum in the absence of an actual observation of either its position or its momentum (and both cannot yield sharp values simultaneously). Thus an electron or an atom cannot be regarded as a little thing in the same sense that a billiard ball is a thing. One cannot meaningfully talk about what an electron is doing between observations because it is the observations alone that create the reality of the electron. Thus a measurement of an electron's position creates an electron-with-a-position; a measurement of its momentum creates an electron-with-a-momentum. But neither entity can be considered already to be in existence prior to the measurement being made.
What, then, is an electron, according to this point of view? It is not so much a physical thing as an abstract encodement of a set of potentialities or possible outcomes of measurements. It is a shorthand way of referring to a means of connecting different observations via the quantum mechanical formalism. But the reality is in the observations, not in the electron.”
Or, to cite John Archibald Wheeler:
“In today’s words Bohr’s point – and the central point of quantum theory – can be put into a single, simple sentence. ‚No elementary phenomenon is a phenomenon until it is a registered (observed) phenomenon.‘“
Wheeler, J.A. (1983) in “Law without law”, in Wheeler and Zurek (eds.), Quantum Theory and Measurement, Princeton University Press, 182–213.
