is also a solution. This implies, then, that the particle exists in every possible position. When an observer comes and measures the position of the particle, then the superposition is reduced to a single possible wave function. (i.e., formula_26 → formula_27, where formula_27 is any of the possible wave function states.) This idea that a particle's position cannot exactly be known, and that a particle exists in multiple positions simultaneously gives rise to the Uncertainty principle. The mathematical formulation of this principle can be given by