One of the great things about being asked to speak on unusual topics is that putting together a talk on a subject a little outside of your usual range sometimes leads to looking at familiar topics from a new angle. When you do that, sometimes you notice connections between things that you hadn't really thought about before. This happened to me a week ago, when I wound up thinking about the centrality of observers to quantum physics, even in places where you don't usually think about them being quite so important.
The proximate cause of this was that I was invited to give a talk on "Quantum Fiction: The Entanglement of Physics and Literature" at the University of Waterloo's Institute for Quantum Computing, as part of their "Entangled" series of talks making connections between physics and other fields. This was a good deal of fun to put together, and if they post video of the talk at some point in the future, I may do a post here with more about that. My approach to this was to offer a moderately detailed explanation of the problem of quantum measurement and then outline two of the main interpretations that try to explain what's going on: the Copenhagen and Many-Worlds interpretations. Each of those has introduced ideas that have ended up either directly serving as story prompts for fiction, or provided a more diffuse sort of philosophical inspiration for stories and literary techniques.
What struck me as I was doing the comparison between the two was that in both of those interpretations, observers have a critical role to play. This is a well-known feature of Copenhagen-ism (and historically one of its more problematic points...), but I hadn't really thought of Many-Worlds in quite that way before. Putting the two together in the one talk made the parallel jump out at me, and I found it interesting enough to be worth a blog post.
As always when talking about quantum interpretations it's worth noting up front that there are approximately as many versions of these interpretations as there are people who have thought carefully about them. No blog post or public lecture is going to do justice to the full range of these, so what follows will be my particular gloss on these things. And I'm going to skip some approaches completely, for the sake of telling a semi-coherent story about this stuff.
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