Physics.
the principle of quantum mechanics, formulated by Heisenberg, that the accurate measurement of one of two related, observable quantities, as position and momentum or energy and time, produces uncertainties in the measurement of the other, such that the product of the uncertainties of both quantities is equal to or greater than h/ 2 pi, where h equals Planck's constant. Also called indeterminacy principle, Heisenberg uncertainty principle .
[ 1930-35 ]