While exploring variations on Shroedinger's Cat, I came up with the following puzzle:
Define a Schroedinger's Black Box (SBB) as a volume whose contents have no causal connection to an observer A. An SBB is very different from the box containing Schroedinger's cat (call it Schroedinger's Cat Box or SCB), because Schroedinger (observer A) put the cat in the box, along with the apparatus that has a chance of killing the cat -- which means that there is a large causal connection between observer A and the contents of the box. An SBB would, for example, be a region of spacetime that has always been outside the observer's light cone; and it could contain absolutely anything because the wavefunction of whatever might be in the box is completely unknown and unknowable.
It seems that there must be a vanishingly small but finite probability that observer A will find a Schroedinger's Cat apparatus inside the SBB. Finding an electron, photon, or nothing at all must be vastly more likely. But if hidden variables are ruled out by quantum mechanics, whatever becomes apparent at the moment the SBB is opened was only potentially there, not really there, until that moment.
Here is the puzzle: How would one go about calculating the major terms of the probability distribution for all the things observer A might see when he/she eventually does get to peek inside the SBB?
This would seem to be a silly question, but actually we are receiving photons all the time from regions of spacetime so far away that light is just now arriving from those regions for the first time since the Big Bang (or whatever that significant event should be called). Significantly, we do not see different physics in the light from those regions. That suggests two possible explanations: A) we actually do have causal connections with even those regions that seem to have always been outside our light cone, or B) apparatus built using our physics can only detect particles that are consistent with our physics (sort of like the whole universe appears to be vertically polarized if we only look at it through a vertically polarized filter).
I favor B, because it seems consistent with the Many Worlds scenario: an observer can only observe states that are consistent with his world. But I wonder if any kind of experiment or observation could distinguish between the two explanations.
Note that this question/puzzle has a close relationship to this question.