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I studied some more about the relational interpretation of quantum mechanics, and yes, things remain uncollapsed at the largest scales. Local collapse doesn’t create certainty, only consistency, which spreads outwards. Any observers who see a definite state are themselves in an indefinite state — nobody can perceive their own superpositions. In essence, then, I would say this is just a refinement of many-worldsism.

Comment by Supersonic Man — May 19, 2016 @ 7:02 am |

Copenhagenism, meanwhile, is moving forward with a “consistent histories” approach, which defines mathematically the degree to which it is possible to ask definite, as opposed to probabilistic, questions about the state of a quantum system. They say that the EPR reasoning fails because they assumed definite knowledge which is beyond the limit of what can be asked. As with the original Heisenberg uncertainty principle, there are certain combinations of facts where you can’t know both at once — if you’re certain of one then the other must be indefinite — and they say EPR’s logic implicitly relies on knowing two incompatible things.

But I am still not clear about how this mathematical assertion of past consistency can actually create physically consistent outcomes without hidden variables.

Comment by Supersonic Man — May 19, 2016 @ 11:50 am |

So, are quantum phenomena reversible in time, or not? I grew up with the dogma that the only thing that distinguishes forward time from backward time is entropy, and this may still be true, since there’s no proof yet that quantum collapse does so. So can entropy apply to quantum interactions? I think it can.

Entropy was originally defined in terms of heat: as areas of differing temperature blend toward a common level of heat, entropy increases. Nowadays it’s defined in terms of the probabilities of states, with likeliness being measured in terms of how broad a range of possible states are essentially similar to one another. For instance, in a bottle of gas or chunk of metal has a uniform temperature, then at any given moment there’s a huge range of different distributions of energy to individual atoms, but all those specific variations amount to the same overall result. If you specify a state where one corner is much hotter than the rest, you have to be a lot more particular about what sorts of states the system might be in. There’s a narrower range of options and therefore, broadly, a much lower probability. Entropy is the tendency to move from narrow specific states to broadly probable states, and in the macro world, this tendency shows that time moves in one particular direction.

On the atomic scale, it doesn’t seem possible to define this when dealing with an interaction of just two particles, but once there are three or more, some interactions are much more likely than others. If we imagine, say, a helium nucleus being knocked into two deuterium nuclei by a fast neutron, it’s already somewhat difficult (though not implausibly so) to imagine the reverse.

Let’s look at the photoelectric effect: an atom in a solid absorbs a photon and loses an electron, leaving the atom in an ionized state. In reverse, an ionized atom captures a free electron and emits a photon. The thing is, the absorption can handle a broad range of photon energies quite uniformly (above a certain threshold roughly corresponding to the range of visible light — this is why UV is “ionizing radiation” but IR is not), but in reverse, the emission is going to very strongly favor particular energies, producing spectral lines in the emitted light. It’s still statistical, but you’d only have to observe a small number of occurrences before becoming pretty confident of which way time was moving.

So until someone comes up with a much stronger argument to the contrary, I’m going to stick with the straightforward naive interpretation of this: that time has one direction which is absolutely and objectively forward, and that any theories that involve backwards time are to be viewed with great skepticism.

Comment by Supersonic Man — May 28, 2016 @ 2:52 pm |

I am now moving toward a belief that the simplest theory which clears up all the contradictions is that hidden variables exist but are unknowable. And Bell doesn’t disprove their existence, only their detectability. I think this would imply that collapse is an objectively real phenomenon, there are no parallel alternative worlds, and time is unidirectional.

Comment by Supersonic Man — June 21, 2016 @ 10:36 am |