| | The Uncertainty Principle |
 | | In many expositions of the subject, the uncertainty may refer sometimes to a lack of knowledge of a quantity by an observer, or to the experimental inaccuracy with which a quantity is measured, or to some ambiguity in the definition of a quantity, or to a statistical spread in some ensemble of similarly prepared systems. |
 | | Popper argued that the uncertainty relations cannot be granted the status of a principle, on the grounds that they are derivable from the theory, whereas one cannot obtain the theory from the uncertainty relations. |
 | | It must be remembered, however, that the uncertainty in question is not simply a consequence of a discontinuous change of energy and momentum say during an interaction between radiation and material particles employed in measuring the space-time coordinates of the individuals. |
| www.seop.leeds.ac.uk /archives/spr2002/entries/qt-uncertainty (10240 words) |