The Heisenberg uncertainty principle Δx × Δp ≥ h tells us that whenever we try to pin down certain pairs of numbers we can only get so close, and that if we try to get clearer on one of them, i.e., if we try to make Δx smaller so we have a better idea of the position of something, then we will have to get handed back a bigger number for the other number of the pair, and that the amount the two are off by is closely related to h.