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I wonder exactly what "it" is here. Quantum mechanics with the "many worlds" interpretation explains lots of things: it explains all the same things as quantum
by gjm11 13y ago
I wonder exactly what "it" is here.
Quantum mechanics with the "many worlds" interpretation explains lots of things: it explains all the same things as quantum mechanics with some other interpretation. But QM (many worlds) has all the same observable consequences as, say, QM (Copenhagen), so "many worlds" as opposed to Copenhagen doesn't explain anything[1].
But how does that mean that intelligent people shouldn't take the "many worlds" interpretation seriously?
Consider two "interpretations" of Newtonian mechanics. One says that the world mechanically obeys Newton's laws. Another says that the world is controlled by incorporeal angels who are very fond of Newton's laws and always freely choose to push the universe around in such a way that those laws are obeyed. These two interpretations have the same observable consequences (namely, a universe in which Newton's laws always hold), but that doesn't make it surprising if intelligent people take the "mechanical" version of it seriously.
Nor, actually, does it make it surprising if intelligent people take the "angels" version seriously. What (at least for me) makes that option hard to take seriously is its gratuitous complexity: it has the same observable consequences as the "mechanical" system but, at least in my view, is vastly more complicated -- if you wanted to describe such a universe completely you'd need to do all the same work as for the "mechanical" version and then go on to set down everything about the angels' nature, personalities, etc.
In much the same way, you might choose to prefer "many worlds" or Copenhagen or some other specific interpretation of QM on the grounds of simplicity. "Many worlds is simplest because it avoids notions of 'measurement' and 'collapse' that do no real work, and just says that everything obeys Schroedinger's equation all the time." Or: "Many worlds is horribly complex because it involves all those extra worlds we never observe."
So if you mean: "The many-worlds interpretation of QM explains nothing more than any other interpretation of QM does, and therefore it's surprising that intelligent people take the many-worlds interpretation seriously", I think that's wrong. But perhaps what you're surprised that people take seriously is some other thing like, e.g., some particular application of the anthropic principle that appeals to "many worlds"?
[1] Actually, that's maybe slightly debatable; it depends on fine details of what you understand by "explain". For instance: any theorem in pure mathematics is logically necessary[2] and therefore has no observable consequences that you couldn't derive without it -- but it still seems reasonable to say, e.g., that a proof that even-length palindromes have to be multiples of 11 "explains" why I've never seen a palindromic prime number with 4, 6, 8, ... digits. So the fact that QM (many worlds) has no extra observable consequences beyond "uninterpreted" QM might not be enough to guarantee that it doesn't explain anything.
[2] Given whatever axioms you start with.
- furyofantares 13y agoYou seem to be suggesting that you have to pick some interpretation. Am I misreading? Why do you have to take any interpretation seriously if it does not imply any observable consequences?
- chrislipa 13y agoWhile there are Occam's razor and complexity arguments concerning the relative merits of the Many Worlds Interpretation and the Copenhagen Interpretation, I think this is at best a weak argument. Because, who knows? We could actually be living in a world with very complicated physics. However, there's a different flaw that I believe completely torpedoes the Copenhagen Interpretation: the Copenhagen Interpretation is not a fully specified theory because it never actually gets around to defining when a measurement is performed. What algorithm can an experimenter run to tell when a measurement takes place? There is none. When a system is considered to be "measured" is always determined with the help of human judgement ex post facto, and alway in such a way as to fit the experimental outcome. If proponents of the Copenhagen Interpretation ever proffered such algorithm to determine when a measurement takes place, then at least we'd have something testable, even if the test were outlandish. But as it is now, the lack of such concrete specification makes the Copenhagen Interpretation unfalsifiable with respect to the Many Worlds interpretation. Besides that, there are a couple other weaker reasons to be very suspicious of the Copenhagen Interpretation. It doesn't seem to address in any way the fact that experimenters and detectors are a part of physics themselves. If you believe that consciousness arises from physical processes happening inside of the universe, it's very hard to imagine how the Copenhagen Interpretation would compute and explain (even in theory) the physics of what's happening inside of the brain. [1] And if waveform collapse actually occurred, it would be the only known law of physics that's non-local, inherently random, has a preferred reference frame (breaking relativity), destroys information, and violates CPT symmetry. This rule is not like the other rules. [1] - There actually is a serious school of thought that conscious beings brings the universe into existence, rather than the other way around. I don't know of any experimental evidence for or against this theory, but I'm personally not a big fan of it because the Kolmogorov complexity required to fully specify the theory is fantastically large, because it would need to fully specify how consciousness operates. Without a corresponding amount of evidence in its favor, there's no reason to elevate this hypothesis among all the others with the same or less complexity.