Karl Popper had this to say about HUP.

"Yet in fact the Heisenberg formula for energy depends neither on wave mechanics nor on Heisenberg's matrix mechanics; nor do we need the commutation relations (which according to Hills are insufficient for the derivation of the formulae). It simply does not depend on the revolutionary new quantum mechanics of 1925-6, but follows directly from Planck's old quantum postulate of 1900:

E = hf.

From this we get immediately

(2) DE = h Df.

By using the principle of harmonic resolving power,

(3) Df approx = 1/Dt,

we obtain from (2) and (3)

(4) DE approx = h / Dt,

which leads at once to

(5) DE . Dt approx = h;

that is to say, a form of Heisenberg's so-called indeterminacy formulae.

In precisely the same way we obtain the Heisenberg formula for position and momentum from Duane's principle (whose analogy to Planck's principle has recently been stressed by Alfred Landé). It may be written

(6) Dpi approx = h / Dqi

According to Landé this may be interpreted as follows: a body (such as a grid or a crystal) endowed with the space-periodicity Dqi is entitled to change its momentum pi in multiples of Dpi approx = h / Dqi.

From (6) we obtain at once

(7) Dpi . Dqi approx = h,

which is another form of Heisenberg's indeterminacy formulae.

Considering that Planck's theory is a statistical theory, the Heisenberg formulae can be most naturally interpreted as statistical scatter relations, as I proposed more than thirty years ago. That is, they say nothing about the possible precision of measurements, nor anything about limits to our knowledge. But if they are scatter relations, they tell us something about the limits to the homogeneity of quantum-physical states, and therefore, though indirectly, about predictability.

For example, the formula Dpi . Dqi approx = h (which can be obtained from Duane's principle just as DE . DT approx = h can be obtained from Planck's principle) tells us, simply, that if we determine the coordinate x of a system (say, an electron) then, upon repetition of the experiment, the momentum will scatter.

Now how can such an assertion be tested? By making a long series of experiments with a fixed shutter opening Dx and by measuring, in every single case, the momentum Px. If these momenta scatter as predicted, then the formula has survived the test. But this shows that in order to test the scatter relations, we have actually measured, in every case, px with a precision far greater than Dpx; for otherwise we could not speak of Dpx, as the scatter of px.

Experiments of the kind described are carried out every day in all physical laboratories. But they refute Heisenberg's indeterminacy interpretation, since measurements (though not the predictions based upon them) are more precise than this interpretation permits.

Heisenberg himself noted that such measurements are possible, but he said that it was 'a matter of personal belief' or personal taste' whether or not we attach any meaning to them; and ever since this remark they have been universally disregarded as meaningless. But they are not meaningless, for they have a definite function: they are tests of the very formulae in question; that is, of the indeterminacy formulae qua scatter relations.

There is, therefore, no reason whatever to accept either Heisenberg's or Bohr's subjectivist interpretation of quantum mechanics. Quantum mechanics is a statistical theory because the problems it tries to solve-spectral intensities, for example -are statistical problems. There is, therefore, no need here for any philosophical defence of its non-causal character."

Remember that I'm not agreeing by presenting it. To me the Copenhagen definition can stand on its own, but then again. It all goes back to a feeling I have that there can be several definitions that may be able to describe reality. So I must be open for alternatives, right?

So far reality makes a fool out of me.

At least it gives me a headache

)