Originally posted by humy
personally, although I am uncertain of the validity of the pilot-wave interpretation of quantum mechanics, I still favour it over the Copenhagen interpretation which I think is erroneous in its logic (don't have a problem with something being causeless. Just think we should be ve ...[text shortened]... gen interpretation and the pilot-wave interpretation is just one of the realist interpretations.
Interesting that in their fluid model the bit of fluid that bounces around bounces around on a surface just short of having waves on it when the particle is absent but waves appear when the droplet is present. This is strongly reminiscent of vacuum polarisation in quantum field theory.
The problem with the Copenhagen interpretation is that it doesn't say anything. It essentially denies the reality of, well, reality. I think it is overly influenced by continental idealist philosophy and gives "conscious" observers too much of a role. Also it relies on a set of observations that can't be made. One makes a momentum measurement which exactly determines the momentum of a particle how exactly? Detectors in particle physics experiments determine the momentum of a particle by measuring the length of the ionisation trail it leaves in a detector. This is not a single observation. There is a similar problem with position measurements. What one sees then is a cascade of electrons caused by the interaction of the incoming particle with an electron in the detector. So what one measures is the position of the scattered electron, not of the actual particle which in principle could be half way across the universe (in practice not as the probability of interaction goes down as 1/r^2 for electromagnetically mediated interactions).
The problem I have with the pilot wave interpretation is that one has the wavefunction as the pilot wave and the particle guided through it. But everything in the theory is written down in terms of the wave. Including interactions. In order to make a measurement one has to have some kind of interaction. But that interaction is governed by the wave and not the particle. So all one ever sees is the wave and one never sees the particle. So what is the point of the particle?
John Bell was of the opinion that pilot wave theory was identical to the many universes interpretation and I think he is right. The piloted particle (piloton?) is a marker to tell you where the particle "really" is and fulfills the same role as the partitioning of the wavefunction of the universe in the many universes interpretation.
John Bell wrote an excellent book (actually a collection of his papers on this subject) called "Speakable and Unspeakable in Quantum Mechanics" which as these things go is accessible, at least to the regular posters in this forum. I strongly recommend it.