Heisenberg’s uncertainty principle
is a fundamental property of quantum systems,
not merely a limit to how small a thing we can measure.
The illustration represents the work of Earle Hesse Kennard and Hermann Weyl.
The standard deviation of position (sigma sub-x)
multiplied by the standard deviation of momentum
(sigma sub-p) is greater than or equal to half the reduced Planck constant.
See also in The book of science:
Readings on wikipedia: