Quantum Mechanics 3:9 Quantum Mechanics 4:9 »

Quantum Mechanics

The Uncertainty Principle


In 1927, Heisenberg predicted that:

In this formula,  x refers to the inherent uncertainty in a measurement of the position, 'x',  p refers to the inherent uncertainty in a measurement of the momentum, 'p' and 'h' is the by now familiar Planck constant.


Heisenberg made one more fundamental and long-lasting contribution to the quantum world – the uncertainty principle. He showed that quantum mechanics implied that there was a fundamental limitation on the accuracy to which pairs of variables, such as (position and momentum) and (energy and time) could be determined. This flew in the face of the traditional wisdom of determinism carried over from Laplace's times.

If a 'large' object with a mass of, say, 1g has its position measured to an accuracy of 1 , then the uncertainty on the object's velocity is a minute 10-25 m/s. The uncertainty principle simply does not concern us in everyday life. In the quantum world the story is completely different. If we try to localize an electron within an atom of diameter 10-10 m the resulting uncertainty on its velocity is 106 m/s!


Related Laureate

 The Nobel Prize in Physics 1932 - Werner Karl Heisenberg »    

Copyright © Nobel Media AB 2014