Decoherence, Incoherence, Elucidation
Dave Price
A flurry of poorly-written news briefs, replete with claims of time travel made possible and proof of parallel universes, have been spawned by the announcement by Oxford scientists that a mathematical model of the Many Worlds Interpretation is more robust than thought. Predictably, perhaps the best explanation of what MWI means comes from a Slashdot commenter:
The remaining issue in a theory of quantum + decoherence is that the classical states have the right probabilities, but there is still nothing to explain why we observe a particular classical state (photon measured spin-up instead of spin-down). However the (ad-hoc) postulate of wavefunction collapse, no longer being necessary to explain how the probabilities arise, can in fact be entirely removed if we allow that the global superposition never collapses.It's odd to think of the Universe we experience as a superposition, but that does seem to be the implication of our current understanding of quantum mechanics.
Thus, a local observer (e.g. an instrument or a human) perceives a single outcome only because they are a participant in this "global superposition" (the superposition of the entire universe). The wavefunction of the universe as a whole evolves deterministically.
Why do some of these people seem to think that this is a 'simple' idea, especially when compared to an idea like God?
It's really weird. Materialism (the philosophical position) was basically a superstition developed in the mid to late 1800s based on the very poor science of the time. Science completely abandoned materialism, but materialism didn't abandon science. The result is some very weird mental contortions.
Has it occurred to anyone that the idea that everything happens doesn't do very well against Occam's razor, especially when stated in the "don't unnecessarily multiply entities" form?
Failing that, haven't these people learned frp, experience that a theory in which every outcome is a trivial consequence is not usually a correct theory? Or, put more simply, you should be careful about theories which prove too much?
"Why do some of these people seem to think that this is a 'simple' idea, especially when compared to an idea like God? "
If you can posit god, then I can simply posit overall brute fact, and explain just as much just as simply: and perhaps less so.
"Science completely abandoned materialism, but materialism didn't abandon science."
That's news to science, for which methodological materialism is not only the norm, but probably the only viable option.
"Has it occurred to anyone that the idea that everything happens doesn't do very well against Occam's razor, especially when stated in the "don't unnecessarily multiply entities" form? "
The problem is that QM is known to be real already, and it doesn't do well against anything we are familiar with to begin with.
I think that is the reason it has taken this long to reach the quantum decoherence interpretation. The traditional collapse-of-the-wavefunction interpretation is, and always was, a deus ex whoknowswhat. As bad as it was -- and at least some people recognized how bad it was -- people preferred it to taking the theory at its word.
One of the lessons that Einstein taught us, is to take the theory at its word. That's how he became the creator of relativity. Others (Lorentz and Poincare) had all the pieces, but didn't take them seriously enough to make relatively out of them. However, Einstein hated QM, and presumably didn't put a lot of effort into fixing its problems.
BTW, the guy who first took QM at its word, Hugh Everett, quit physics because no one else took his ideas seriously. He applied the math he had learned to real-world problems and became a multi-millionaire.
First, this what the theory says, and we should listen to the theory. Second, it goes along with the general rule of progress in physics: "Simpler, smaller, weirder."
Of course we all lose our tempers now and then. Dean freely admits to being imperfect in this regard, which is why regulars to this establishment will generally be cut more slack than people who we don't know very well.
Still: behave like an adult, or go find somewhere else to play. Thanks.