I'll genuinely stop on this topic now for a few months, if people want to discuss I'd be happy to on the physics forum. I just don't want to leave the wrong impression.
Originally Posted by Franz Von Peppercorn
Some of physics, or more kindly some interpretations of it, seems to be heading down this kind of intellectual cul de sac. In the We can’t measure it does it really exist?
Just to be clear that's not what the issue with QM is about. Neither the theory nor ideas related to it say things don't exist when they're not being observed. In my career I have encountered nobody who thinks stuff doesn't exist if we can't measure it, even in the most extreme views on QM. I don't think this is even a minority opinion in either physics or its interpretations.
Rather we know
for example that objects aren't really made of particles or fields. Particles and fields are just useful ways of describing certain experimental results. This isn't abstract philosophising as Quantum Mechanics as a scientific theory directly says this. It literally flags/warns you about situations where thinking things are made of particles will lead you to incorrect conclusions.
For example the radiation that comes off certain nuclear reactions, if you attempt to think of that radiation as being made of particles and proceed on that basis you'll make wrong conclusions about how the reaction will proceed. Similarly certain processes in the cores of stars and certain effects in metals can't be explained in particle terms and QM will warn you not to use particle concepts there. Even in cases where you can use the idea of particles, you mightn't be able to use all of it. So for example shining light off a caffeine molecule, QM says that the caffeine can be thought of as a particle and the light can be thought of as particles (photons). However even in that case QM will warn you that you can't use everything we normally associate with a particle. We naturally think of particles as having a size, a mass, some energy, a location and a speed. In the caffeine example QM will tell you that the size and location concepts should just be ignored/aren't applicable. In other cases it might be the mass concept you should forget about.
Even worse sometimes a concept can apply but give varying answers. For example in a beam of light the "Number of Photons" concept does apply, but sometimes when you measure it you find 45 photons, the next second 72 photons and this is the same unchanged beam of light. So the concept is fine to use, but clearly the light isn't actually made of a specific number of photons.
These are scientific predictions and QM is providing an experimentally testable guide to when certain concepts (particles, fields, energy, momentum, etc) are valid and okay to use and when they are not. It's not an intellectual cul de sac, it's something you have to directly acknowledge as being shown from experiments.
Obviously then the underlying stuff doesn't care about our concepts ultimately, since any of them could fail to apply in different situations. Unfortunately we just don't know what are the sensible concepts/descriptions for the fundamental stuff and there are strong reasons (in the form of mathematical theorems) to think we basically can't understand them.
Not being able to grasp something is completely separate from thinking it doesn't exist.