Warren,
You accuse Quantum Physics of being mere metaphysics and then talk of there being no way "to decide whether positions and momentums are really discrete or not." They aren't discrete and must be considered as a cloud of probability - that's the point - .
There is no pretense that the quantum world as decribed is a real world description and it doesn't matter, because it the theory allows results that correpsodn to to real world behavious to be derived. This is not exclusive to quantum physics - pharmakokinetics describes volumes in the body that are measure in hundreds of mls/kg - impossible of course but no matter as the tecnique allows the prediction of drug concentrations over time.

The point is also that in QP, defining one parameter makes the others more uncertain.
In 'real world' sciences, hard or soft, clever observers have developed ways to avoid the observer effect, because there is no theoretical abberation introduced, just clumsy observing.

John

PS a thermal radiation sensor WILL affect the water drop, as it will absorb more radiation than than in the unobserved state!
PPS Oops, sorry, Ivor said that!