Niels Bohr … understood that the energy of electrons in atoms can take on only certain values, like the energy of light, and crucially that electrons can only jump between one atomic orbit and another with determined energies, emitting or absorbing a photon when they jump. These are the famous “quantum leaps.”
Werner Heisenberg imagined that electrons do not always exist. They only exist when someone or something watches them, or better, when they are interacting with something else. They materialize in a place, with a calculable probability, when colliding with something else. The “quantum leaps” from one orbit to another are the only means they have of being “real”: an electron is a set of jumps of one interaction to another. When nothing disturbs it, it is not in any precise place. It is not in a “place” at all.
It’s as if God had not designed reality with a line that was heavily scored but just dotted it with a faint outline.
Seven Brief Lessons on Physics