One kind of optimal tradeoff minimizes the product of position uncertainty Δ Δ x and momentum uncertainty Δ Δ p x . If we place such a packet at rest it stays at rest: the average value of the position and momentum match a classical particle. However it spreads out in all directions with a velocity given by the optimal momentum uncertainty Δ Δ p x . The spread is so fast that in the distance of once around an atom the wave packet is unrecognizable.