| 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/2π, where h equals Planck's constant. |
| uncertainty principle n. A principle in quantum mechanics holding that increasing the accuracy of measurement of one observable quantity increases the uncertainty with which another conjugate quantity may be known. |
uncertainty principle  (ŭn-sûr'tn-tē) Pronunciation Key
A principle, especially as formulated in quantum mechanics, that greater accuracy of measurement for one observable entails less accuracy of measurement for another. For example, it is in principle impossible to measure both the momentum and the position of a particle at the same time with perfect accuracy. Any pair of observables whose operators do not commute have this property. As defined in quantum mechanics, it is also called Heisenberg's uncertainty principle. Similar uncertainty principles hold for non-quantum mechanical systems involving waves as well. |
