The principle in quantum theory stated by Werner Heisenberg in 1927 which says that it is not possible to simultaneously determine the position and momentum of a particle. Mathematically, this means that the momentum observable P and the position observable X do not commute or, more precisely Δ‎_ψ‎(P)Δ‎_ψ‎(X)≥ℏ/2, where Δ‎_ψ‎ denotes dispersion of a wave function ψ‎, and ℏ is the reduced Planck’s constant.