There is an interesting and very informative conversation going on here about the implications of quantum mechanics and the plausibility of the multiple worlds interpretation. The discussion was seeded by a brief, informative, and mercifully clear article by physicist Stephen Barr. Barr is also participating in the discussion for the next couple of days, so check it out.
This particular bit of the exchange caught my attention, making me wonder about its implications for the project of Speculative Realism (particularly Quentin Meillassoux‘s complaints about “correlationism”):
Steve Barr to Josh Weiner:
I think I know what is bothering you, Josh. As I said in reply to Wallace Forman (in the third paragraph), it all comes down to what the wavefunction of a system is. One would like to be able to say that it is just a straightforward description of what is happening in the world, of the world as it really is, apart from what you or I know about it. That leads straight to the Many Worlds picture, because the wavefunction typically contains descriptions of many alternative branches. In the traditional or Copenhagen interpretation, one has a more modest view of what the wavefunction is: It is not simply “the world as it is”, but rather it encodes what some observers know or are in a position to assert about the world. that is why heisenberg himself said that the mathematics of quantum mechanics “represents no longer the behavior of elementary particles, but rather our knowledge of this behavior”. And it is why Rudolf Peierls said, “the quantum mechanical description is in terms of knowledge.”
That raises a very important question — which, I think, is your question: What DOES describe “the world as it really is”? Even if the wavefunction does not describe it, there must be some comprehensiove and complete and accurate description of physical reality — call it the “God’s eye view of things” (even though I don’t want to drag God back into the discussion).
In other words, what IS really going on when no one is looking? What if beings such as ourselves had never evolved? What about regions of the universe that no human or other sentient organism is ever going to observe or make measurements of? What about what will be happening in the universe after all life has died out? Good questions! The wimpy answer is that science cannot speak about things that cannot be observed, and what is going on in places that will never be observed is, by definition, something that cannot be observed! But that seems a pretty unsatisfactory answer. The traditional Copehagen interpretation doesn’t give an answer. I have an answer that satisfies me, and I give a very brief sketch of it in my reply to jrd261. Here I will only say that I think that even in the context of the traditional interpretation of quantum mechanics there does exist an answer to the question “what is really going on in the world even when no observers are looking”. In other words, the traditional interpretation does NOT commit one to some form of subjectivism or Berkeleyan idealism, but can be consistent with a robust philosophical “realism”. But this is a tricky business, and probably beyond what can be discussed in such a forum.
FYI, this is, I think, the relevant part of Barr’s answer to jrd261, mentioned above:
In particular one could take the view that whenever there is a branching of the wavefunction (which happens when different parts of the wavefunction “decohere” from each other, in the technical jargon) all consciousness in the universe proceeds down just one branch. The wavefunction would continually branch, exactly as MWI says, but there would never be a situation where the same observer existed in several conscious versions in distinct branches. In this picture, the wavefunction itself is constantly branching, like train tracks; and what happens at the “collapse of the wavefunction” is not really any change in the wavefunction — all the tracks are still there — but rather all consciousness proceeds down a single track, so to speak. (What I have just described is my own speculative view of quantum mechanics, for what it’s worth.)