Originally Posted by **MBW** My previous post was leading up toward asking if UP always involves a time verses space combination,
or to put it another way, is UP fundamentally an issue related to space-time combinations? |

Heisenberg's UP is a direct consequence of the (pure) mathematics of Schrodinger's equation or the paired operators.

For two observables A and B which have representative operators a and b in the governing equation (a and b are what PMB means by the momentum wave function) there are two possibilities.

a and b commute (may be taken in any order) in the equation

Then the two observables may be measured simultaneously.

If they do not commute the equation does not possess a complete set of eigenfunctions in common to both observables.

Then measurement of one observable will affect the value of the other.

This is all very general and leads to the Schwarz inequality in pure maths (there are other equations with this property even in classical mechanics).

Heisenberg's UP can be derived from the Schwarz inequality, if you want to look this up.

Remember that Schrodinger's equation is an equation of motion not directly momentum, position, time or energy.

Look at the dimensions of the wavefunction psi.