**Heisenberg's uncertainty principle** In quantum physics the Heisenberg uncertainty principle states that you cannot measure at the same time the position and the momentum of a particle accurately.

If you can measure the position accurately you cannot measure the momentum accurately and vise versa.

Another way to state the Heisenberg uncertainty (indetermination) principle is:

No predictive laws exist containing references to the simultaneous position and momentum of a particle.

So instead of saying that it is uncertain it is called indeterminate: it may be certain (who knows?) but you just cannot determine it simultaneously.

Heisenberg indetermination relationship:

ΔfΔg >= ½<[f,g]>

The uncertainty in the value for observable f or g is greater or equal to half of the average value of the commutator of operators f and g. Hence, if f and g commute they can be simultaneously accurately measured.

__See also:__ Uncertainty principle

http://en.wikipedia.org/wiki/Uncertainty_principle#Matrix_Mechanics The Uncertainty Principle

http://hyperphysics.phy-astr.gsu.edu/Hbase/uncer.html